My macbook pro 2015 is getting slower. Its already SSD. I wonder why. Is it the OS? Maybe its the fan that I need to clean? If it is both I’m going to just make this into a Linux laptop.
For my 2010 MBP, I'm running Linux on it and it's really brought it back to life. Especially with the 5.4 LTS kernel and Ubuntu 20.04 LTS, both with support until 2025. I say go for it, you'll have a ton of fun on it.
And if making it look like macOS is your thing, here's how I got mine looking: https://i.imgur.com/QgyRvrD.png
(Unfortunately the dGPU on the machine appears to have developed a fault which might put it into retirement for good)
IIRC 2015 was the last MBP with good Linux support (my 2016 MBP didn't have audio or suspend/resume until recently, after I gave up and ditched it), so that might work out well for you.