How to fix recent Silverblue audio and suspend issues on X1 Carbon Gen 7

Short answer:

$ rpm-ostree install alsa-firmware

Long answer (which may not be 100% accurate but summarizes my research trying to fix this) :

Skylake+ laptops can, apparently, have advanced audio DSPs which require firmware images, and very recent kernels operate those DSPs in a way that requires external firmware. This firmware is part of the alsa-firmware package (which is not part of SB by default), not the usual linux-firmware package (which is).

Without this firmware your system will have no audio, but it will also freeze on suspend. Or at least my laptop’s suspend issue went away coincidentally for me when I installed the alsa-firmware package.

Incidentally the particular firmware in question is open source, and is part of the “Sound Open Firmware” project.