I have a "Dell XPS 13 2-in-1 7390" with a "Killer(R) Wi-Fi 6 AX1650i 160MHz Wireless Network Adapter (201NGW), REV=0x338" card. When booting with Linux 5.4-rc6 (yes, from yesterday), it seems that the firmware crashes and never provides workable wifi. The relevant lines from dmesg are here:

# journalctl -b -2 | grep iwlwifi
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: enabling device (0000 -> 0002)
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-Qu-b0-hr-b0-50.ucode failed with error -2
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-Qu-b0-hr-b0-49.ucode failed with error -2
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: TLV_FW_FSEQ_VERSION: FSEQ Version: 43.2.23.17
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Found debug destination: EXTERNAL_DRAM
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Found debug configuration: 0
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: loaded firmware version 48.4fa0041f.0 op_mode iwlmvm
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Detected Killer(R) Wi-Fi 6 AX1650i 160MHz Wireless Network Adapter (201NGW), REV=0x338
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Applying debug destination EXTERNAL_DRAM
Nov 04 18:37:19 lightning kernel: iwlwifi 0000:00:14.3: Allocated 0x00400000 bytes for firmware monitor.
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Collecting data: trigger 15 fired.
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Start IWL Error Log Dump:
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Status: 0x00000000, count: 1293753132
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Loaded firmware version: 48.4fa0041f.0
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x1BAE2A3D | ADVANCED_SYSASSERT          
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x7473B3B2 | trm_hw_status0
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xD7B74DD3 | trm_hw_status1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xC5450046 | branchlink2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x3135B253 | interruptlink1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x5E6644BC | interruptlink2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xCB78B7C8 | data1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x7D3859AA | data2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x226D363E | data3
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x4BCA4621 | beacon time
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xA9F777AF | tsf low
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x63802C24 | tsf hi
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x42C4A9EF | time gp1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xDF4BFC96 | time gp2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x991EDE29 | uCode revision type
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x92207155 | uCode version major
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x9A1EBD03 | uCode version minor
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x70B13062 | hw version
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xEDE9B24A | board version
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x171ECE71 | hcmd
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x43641494 | isr0
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x023023C1 | isr1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x3D7BD4CA | isr2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x318F056E | isr3
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00D0D16E | isr4
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x51531642 | last cmd Id
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x38A76256 | wait_event
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x5C7501B2 | l2p_control
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x1EE5C886 | l2p_duration
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x28C9088F | l2p_mhvalid
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x9515A415 | l2p_addr_match
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xD62FDFB7 | lmpm_pmg_sel
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x43E4AE64 | timestamp
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x9246FE7D | flow_handler
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Start IWL Error Log Dump:
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Status: 0x00000000, count: 7
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x201013F1 | ADVANCED_SYSASSERT
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | umac branchlink1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xC008D49C | umac branchlink2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | umac interruptlink1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | umac interruptlink2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000003 | umac data1
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x02000300 | umac data2
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x01300504 | umac data3
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000030 | umac major
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x4FA0041F | umac minor
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x0000606E | frame pointer
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xC0887F58 | stack pointer
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | last host cmd
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | isr status reg
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Fseq Registers:
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000003 | FSEQ_ERROR_CODE
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | FSEQ_TOP_INIT_VERSION
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000000 | FSEQ_CNVIO_INIT_VERSION
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x0000A481 | FSEQ_OTP_VERSION
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00000002 | FSEQ_TOP_CONTENT_VERSION
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xC9FE63BD | FSEQ_ALIVE_TOKEN
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x00984CA0 | FSEQ_CNVI_ID
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0xDDF4EB7F | FSEQ_CNVR_ID
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x02000300 | CNVI_AUX_MISC_CHIP
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x01300504 | CNVR_AUX_MISC_CHIP
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x05B0905B | CNVR_SCU_SD_REGS_SD_REG_DIG_DCDC_VTRIM
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: 0x0000025B | CNVR_SCU_SD_REGS_SD_REG_ACTIVE_VDIG_MIRROR
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: SecBoot CPU1 Status: 0x5fbf, CPU2 Status: 0x3
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Failed to start RT ucode: -110
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Firmware not running - cannot dump error
Nov 04 18:37:20 lightning kernel: iwlwifi 0000:00:14.3: Failed to run INIT ucode: -110

On 5.4-rc5, the driver says:

Nov 04 18:41:13 lightning kernel: Intel(R) Wireless WiFi driver for Linux
Nov 04 18:41:13 lightning kernel: Copyright(c) 2003- 2015 Intel Corporation
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: enabling device (0000 -> 0002)
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-50.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-49.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-48.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-47.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-46.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-45.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-44.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-43.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-42.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-41.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-40.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: Direct firmware load for iwlwifi-QuQnj-b0-hr-b0-39.ucode failed with error -2
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: no suitable firmware found!
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: minimum version required: iwlwifi-QuQnj-b0-hr-b0-39
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: maximum version supported: iwlwifi-QuQnj-b0-hr-b0-50
Nov 04 18:41:13 lightning kernel: iwlwifi 0000:00:14.3: check git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git

but it can be coerced into working by using this command to (a bit brutally) make it aware of which firmware to load:

sudo cp /lib/firmware/iwlwifi-Qu-c0-hr-b0-48.ucode /lib/firmware/iwlwifi-QuQnj-b0-hr-b0-48.ucode

That files md5sum is this:

16e59dd2792af9a569a958ff92bd3679  /lib/firmware/iwlwifi-QuQnj-b0-hr-b0-48.ucode

(identical to iwlwifi-Qu-c0-hr-b0-48.ucode from linux-firmware rev 11bdc57)

x-ref: https://gitlab.com/emrose/xps13-7390_debian/blob/master/opt/scripts/fix-wifi-and-bluetooth.sh