Is there any way to submit a PC Sekiro run while on Linux? As Live-split doesn't work, I'm unsure what to do.

Thanks for any help!

Yes, it is possible. You need to run livesplit (the .exe) in the same wine prefix as the game. I know someone is working on a tool to auto-install it, I personally use a script for now. We can give you more information on discord if you struggle with it.