Ah - it's in the original thread by Zaela:
https://www.project1999.com/forums/s...=218666&page=6
And here's the link copied to a thread that will hopefully show in searches for "p99 steam deck middlemand" lol:
https://github.com/rtrajano/p99_login_helper
Good luck!
*edit - i have not tried using this.
-Mcoy