I am running Bazzite 40 on a system with an RTX 4080. Up until yesterday, I was connecting computer -> Samsung HW-Q900C soundbar -> Samsung Q90C TV. I learned that the soundbar doesn't have HDMI 2.1 ports which is why I hadn't been able to get 120Hz, so I changed my setup to computer -> TV + soundbar -> TV (eARC).

Now, I do have 120Hz, but I lost a bunch of other options in my display settings, including HDR. The only options I can set there now are resolution, orientation, refresh rate, and scale. I suspect this is an issue with the TV communicating its capabilities in a way the OS doesn't understand, but I'm not sure how to fix or work around it. Can anyone suggest a fix? Is there a setting I can change on the TV or maybe an app I can run on the computer to manually set the TV's capabilities?

Update: Just discovered kscreen-doctor. Here's the output:

Output: 445 HDMI-0
	enabled
	connected
	priority 1
	HDMI
	Modes:  446:3840x2160@60!  447:4096x2160@120  448:4096x2160@100  449:4096x2160@60  450:4096x2160@50  451:4096x2160@30  452:4096x2160@24  453:4096x2160@24  454:3840x2160@144  455:3840x2160@120*  456:3840x2160@100  457:3840x2160@60  458:3840x2160@50  459:3840x2160@30  460:3840x2160@25  461:3840x2160@24  462:3840x1600@144  463:3840x1600@120  464:3840x1600@60  465:3840x1080@144  466:3840x1080@120  467:3840x1080@60  468:2560x1440@120  469:2560x1080@144  470:2560x1080@120  471:2560x1080@60  472:1920x1080@144  473:1920x1080@120  474:1920x1080@100  475:1920x1080@60  476:1920x1080@60  477:1920x1080@50  478:1920x1080@30  479:1920x1080@25  480:1920x1080@24  481:1680x1050@60  482:1600x900@60  483:1440x900@60  484:1280x1024@75  485:1280x1024@60  486:1280x800@60  487:1280x720@60  488:1280x720@60  489:1280x720@50  490:1152x864@75  491:1024x768@75  492:1024x768@70  493:1024x768@60  494:800x600@75  495:800x600@72  496:800x600@60  497:720x576@50  498:720x480@60  499:640x480@75  500:640x480@73  501:640x480@60 
	Geometry: 0,0 3840x2160
	Scale: 1
	Rotation: 1
	Overscan: 0
	Vrr: incapable
	RgbRange: unknown
	HDR: incapable
	Wide Color Gamut: incapable
	ICC profile: incapable
	Color profile source: incapable

SOLUTION: Turns out this was my goof. I was trying to set up auto-login on my user account. In doing so, I set it to automatically log in to Plasma (X11) instead of Plasma (Wayland). Odd that the default option in that dropdown is not the one you’re currently using, but 🤷‍♂️.

What I’m now trying to figure out is why I can’t set auto-login for Plasma (Wayland). The Apply button is disabled. 🤔

Thanks to everyone who shared ideas.