There is a game I play (Undertale Yellow) that only works correctly under Proton 10.0-2d, but since it got superseded by Proton 10.0-3, the option is no longer available through Steam. I tried following the instructions that came with the source code in the terminal, but it doesn't seem to be installed after checking both Steam and my Proton versions directory. I've attached files for both the build instructions and what I put in my terminal, respectively, in case I did anything wrong:
#(Partially solved?) Need help compiling Proton 10.0-2d from source
fiery radish
fiery radish
(Partially solved?) Need help compiling Proton 10.0-2d from source
UPDATE: its_sudo found a fork of Proton called GE-Proton10-11 that fixed my screen flickering issue on Undertale Yellow, it was already compiled so all I had to do was drop it into ~/.steam/steam/compatibilitytools.d after extracting it. Here's the github link of the project for anyone curious: https://github.com/GloriousEggroll/proton-ge-custom/releases
However, since I didn't technically solve my issue of compiling Proton from source, how would I label this post, and should I keep it open?
severe halo
However, since I didn't technically solve my issue of compiling Proton from sour...
If you still need help, keep it open, simple as that.
And for compiling proton, have not seen that mentioned often, try in #💻coding too, someone active there might be able to help. 
fiery radish
Alright, I don't need help anymore so I'll just close this for now 👍