This is an AMD model, with a Realtek ALC3254 and "Digital-array microphones in camera assembly) (specs from https://dl.dell.com/content/manual7958950-alienware-m17-r5-amd-setup-and-specifications.pdf?language=en-us&ps=true)

[mendie@aw-m17 ~/rpmbuild/SOURCES]$ lspci -nn | grep Audio
03:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 21/23 HDMI/DP Audio Controller [1002:ab28]
36:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Rembrandt Radeon High Definition Audio Controller [1002:1640]
36:00.5 Multimedia controller [0480]: Advanced Micro Devices, Inc. [AMD] ACP/ACP3X/ACP6x Audio Coprocessor [1022:15e2] (rev 60)
36:00.6 Audio device [0403]: Advanced Micro Devices, Inc. [AMD] Family 17h/19h HD Audio Controller [1022:15e3]

Audio output is ok, but the internal microphone is not shown - only the combo headphone/microphone jack. 

It seems this is the same problem as https://bbs.archlinux.org/viewtopic.php?id=278886, and also reported in https://bugzilla.kernel.org/show_bug.cgi?id=216270 and https://bugzilla.kernel.org/show_bug.cgi?id=216299.

modifying acp6x-mach.c to include the device shows a microphone, which can now be used

--- a/sound/soc/amd/yc/acp6x-mach.c
+++ b/sound/soc/amd/yc/acp6x-mach.c
@@ -143,6 +143,13 @@ static const struct dmi_system_id yc_acp_quirk_table[] = {
                        DMI_MATCH(DMI_PRODUCT_NAME, "21CL"),
                }
        },
+       {
+               .driver_data = &acp6x_card,
+               .matches = {
+                       DMI_MATCH(DMI_BOARD_VENDOR, "Alienware"),
+                       DMI_MATCH(DMI_PRODUCT_NAME, "Alienware m17 R5 AMD"),
+               }
+       },
        {}
 };

This device only has 2 speakers, so https://github.com/alsa-project/alsa-ucm-conf/issues/215 doesn't seem to be a problem, although I will look into this as well.