- Fractional scaling: That's because X11 itself does not support it. Many older Windows apps also have problems with fractional scaling.
- HDMI 2.1: The HDMI Forum blocked it, as they don't want the details of HDMI 2.1 publically available. If you can, use DisplayPort, which is an actual open standard, and is better anyway. Nvidia works because they implemented it in closed-source firmware instead. https://www.phoronix.com/news/HDMI-2.1-OSS-Rejected
Strangely enough Plasma was able to handle this regardless (guess it was misreporting the resolution to X11 app or something like that to make it work ?) it was a Gnome/Wayland thing.
DisplayPort isn't an option - the TV only has HDMI in and converters suck (they crash constantly, even the expensive ones)
- HDMI 2.1: The HDMI Forum blocked it, as they don't want the details of HDMI 2.1 publically available. If you can, use DisplayPort, which is an actual open standard, and is better anyway. Nvidia works because they implemented it in closed-source firmware instead. https://www.phoronix.com/news/HDMI-2.1-OSS-Rejected