If this is Linux, I’m pretty sure that you can use RandR (or whatever Wayland’s analog is, if this is Wayland) to crop the visible area to whatever aspect ratio you want. Probably on Wayland the wlr-randr command can do it on wlroots-based conpositors.

I’ve done so before on X11 with an HMD that extended into the edges of my visual field, where I wanted everything in the (crisp, clear) center.

searches

Looks like it:

man.archlinux.org/man/wlr-randr.1.en

--mode | --custom-mode     <width>x<height>[@<refresh>Hz]

Set output resolution and, optionally, refresh rate.

--pos <x>,<y>

Position the output with absolute layout coordinates.