Far and away the biggest thing I can recommend: Use the same distro yourself. If there ever are issues, you’ll almost certainly encounter them first and know how to fix them quickly. Ideally use it yourself for a bit before you put it on your mom’s computer so you can find any initial issues too.
I experienced that only when doing expert things on my system like trying to install new drivers.
I’ve been using 4 different immutable distros for a few years and literally the only “breaking” thing was when UBlue distros moved to Fedora 42, which no longer allowed you to use the ostree admin unlock --hot-fix hack to directly modify your system and made you build your own modified variant using their GitHub template repo.
I’m actually moving my wife to a UBlue distros specifically because I set it up remotely and it just auto updates.
I will warn however that Flatpaks can be a nightmare for basic things like browsers if you want to do things like use a webcam, microphone, or, god forbid, a USB device. Make sure you manually set that up in the (probably flatpak) you’re using before handing it over (probably by using Flatseal).
Bluetooth protocol support for audio is a bit of a mess, and many Bluetooth devices (especially knock off or no-name budget brand headphones/headsets) skimp on applying the standard properly.
Absent the absolute latest Bluetooth standard support (5.3 or better), you’re usually limited by the protocol to very poor quality audio. It gets even worse of your device shows up as a headset inst4ad of heaphones/speaker since it has a mic return channel crammed into the very restricted bandwidth too. The way (mostly quality) vendors have worked around this prior to the latest Bluetooth protocol versions was to use raw data channels with negotiated compression formats and a special “escape hatch” protocol supported by Bluetooth (A2DP). Both sides had to negotiate a shared compression algorithm and implement it for sending the compressed audio so it could be decided at the destination. Poorer quality or older headphones, and older Bluetooth Linix stacks didn’t do this very well.
Not sure if any of that is applicable, but in general Bluetooth is always worse quality than wired because of bandwidth restrictions. And until Bluetooth 5.3 that added LE Audio and a related very efficient audio compression algorithm, it was a compatibility crap shoot.