I just went through trying to install Linux on my 2015 15” retina MacBook Pro (model 11,5 with Radeon dGPU) and it was not usable. Every distro I tried (Ubuntu, Pop OS, Fedora, and NixOS) had severe Bluetooth instability (most times the computer booted, Bluetooth worked for about 15 seconds after boot and then it would die completely until the next reboot). Graphics switching seems non functional on this model as well.
I’m looking for an alternative when Apple stops supporting Mac OS on this machine, and I was surprised at how flakey the hardware was in Linux on a 7 year old machine.
I have a 13" Macbook from the same year and it pretty much just works with Nixos. There was a bit of trouble getting Bluetooth working, but as I'm not using it much can't say for it's instability.
What is graphics switching, there is one (integrated) GPU, no?
Also had to tweak kernel with a recent Ryzen GPU a few years ago on a desktop, but after that it worked. (Now the tweak isn't required anymore.)