I wasn't going to reply, but when I thought about it, you can install wayland on top of linux.
The kind of benefit you're getting out of this is better driver support (from the kernel) & less resource usage (lightweight distro + wayland on background = 2GB~ish ram usage).
Also it'd be easier to get Gapps running (if you need it) on waydroid rather than rooting lineageOS TV to do so.
I tried it once & it was more than enough for light gaming, IDK about plex but hardware acceleration is supported since there's no VM tech utilized (nividia isn't supported tho).
Most linux distros with wayland should be enough, but check Wayland install page just to be sure it's well supported (by distro), I see void-linux & ether configured labwc or KDE plasma should fit your needs better.
???
No?
I said you can run way waydroid on a Wayland Desktop to natively run streaming apps on your RPI5. (Plex, Youtube, netflix or whatever service you're on)
This has nothing to do with your TV remotes nor hdmi-cec.
(reads description again) oh...
No, IR input support is now integrated into the linux kernel [BPF] & can be manually done with LIRC,
Well I don't have a RPI to test this nor use my TV remote to control media, just for volume;
Can't say for sure if Rasbarian supports most remotes ether, but LineageOS TV Does (Scroll),
Sorry, I can't help with that, however, a budget, 2.4GHz, wireless mouse was enough for me, maybe KDE Connect or Unified Remote (non-free) can help if you wanna use your phone instead.
CEC support is up to the (media) software &or OS you're using, waydroid is a container-like "runtime" to boot android on linux without virtualization, it's not a an OS that supports IR input or shutting your TV with your TV Remote, I don't think most desktop enviroment does support it nor must, KDE Bigscreen might but it's a DE tailored for such use...
So, if launching plex with your TV remote is a priority, then here's Android(TV) & a Custom Recovery (Gapps & Root Flashing) for RPI5 so you can treat it as an android box.
(unoffical tho, seems like LineageOS team into the BananaPi instead)