Sup folks, anyone here a linux user who's had success running 3420 on Linux? want to get back into trying to speedrun this game but I don't use Windows anymore, so i want to see if it's even possible to run 3420 on Linux.

You can run it in Wine or Proton probably, adding the exe to steam and running it with proton worked for me for SourceUnpack but I haven't tried 3420.

Yeah it works, I just installed Source Unpack and added portal.bat as a non-steam game. Then, through steam I checked the box in the "Compatibility" tab to run it through proton-ge.

Side note: borderless windowed mode doesn't seem to work on Linux, as the game seems to just default to Fullscreen, preventing use of Livesplit unless you like staring at your taskbar.

I suppose that makes sense. Also, you've managed to get Livesplit running in Linux? I thought it didn't work.

Livesplit works in Linux under wine, or you can compile LivesplitOne. I've gotten both working in Debian 10 and 11.
What does not work is the autosplitter functionality, so you'd have to use a hotkey to trigger the splits. If anyone has figured out how to make Livesplit work with autosplitter under Linux, I'd love to know. I haven't had to run a Windows machine in about a decade, but I had to build one last month when I decided to speedrun Portal Reloaded. I spent a good couple weeks trying to get Livesplit to talk to SAR in Linux, no luck here.

So, trying out the Source Unpack now, loading Portal.bat as a non-steam game, and setting it to use the latest Proton-GE version gives me a "failed to load the launcher DLL: Module not found" error. Any ideas why this might be?

Whoops, nevermind, I'm stupid and typed 7z e (the one that just dumps every file into one directory) instead of 7z x (the one that unzips everything and keeps filepaths). Now faced with a new issue in that my fonts look awful.