Replay Mod Forums

It is not running any programs, both xdg-desktop-menu and ffmpeg fail to execute even though both exist. Log: https://hastebin.com/isutadufiy.sql

I have no idea how Ubuntu's snaps work because I've never used them nor have I heared much about them but I'm guessing that apps in one snap (in your case the MultiMC5 snap) don't have access to programs outside of that snap.

So you'll either have to install ffmpeg inside that snap (if installing a program inside a snap is even a thing you can do) or just install MultiMC outside of any snap.
There are .deb packages and plain tar archives on their website.

New error using vanilla launcher: https://hastebin.com/ilaqiwugif.sql

You're trying to load the 1.12.1 version of the ReplayMod on Minecraft 1.8.9.

Oops, working now. Thanks for all the help.