This is the best summary I could come up with:

Mozilla Firefox has merged Wayland fractional-scale-v1 protocol support for handling fractional scaling with the web browser on the Linux desktop.

Merged yesterday is the Wayland fractional-scale-v1 support for this fractional scaling that has been successfully tested with the KDE KWin compositor.

Unfortunately at the moment though this Wayland fractional scaling support is disabled by default: for now interested users will need to set the widget.wayland.fractional-scale.enabled preference for enjoying this fractional scaling support.

The Wayland fractional scaling support was tracked via this bug report.

It’s great seeing Firefox finally supporting Wayland fractional scaling!

The fractional-scale-v1 protocol has been enjoying fairly robust support by the numerous Wayland compositors and seeing support within Google Chrome/Chromium web browser since earlier this year and also other desktop software like the MPV video player rather than being limited to integer-based scaling.

I’m a bot and I’m open source!

I hardly know anything about the graphics processing / posix, can someone explain why applications need to handle it themselves?