

MKVToolNix has a great cropping feature that completely lossless because it just writes an information into the file how many pixels to leave out.
The massive problem since quite some time is that I’m not aware of any media player respecting this. VLC used to support it but a decade ago suddenly stopped: https://code.videolan.org/videolan/vlc/-/issues/13982
If you have the originals, maybe encode them again. HandBrake has a nice preview feature.
Get them a Steam Deck and target only Steam Linux Runtime 3.