I have a 2011 MBP running Mint and it works great. Not unreasonably slow at all. I wish the author had at least tried to use Linux, maybe it was the learning curve.
The resulting laptop did have Linux installed, it's right there in the screenshot. The point of the post is showing how the modular nature of Framework boards can be used in all sorts of cool and unexpected ways.
The author said the original hardware was dead, so I don't think it could run anything at all, at any speed.
I was also running mint on a 2011 MacBook Pro. I bought it new in 2011 and used it until early 2023, then the GPU failed for the second time, which requires the logic board to be replaced. It’s a known hardware flaw which will impact all 2011 MBP models with a discrete GPU.