I think it's the first time I'm hitting this issue. I use Steam ROM Manager to manage my ROM's library inside Steam by means for custom application link generation (I think everybody realizes how this works by now). I then noticed that my games were launching fine outside Steam, using the exact same execution line (excluding the reaper thing) that Steam itself logs in the console (when I start it from console to check what's happening), but they were not launching fine anymore when started from inside Steam. I noticed this is happening just for games whose path contain curly quotes (e.g. "~/.local/bin/steam-yuzu" "/mnt/data/Emulation/ROMs/Super Foo’s Fury.nsp", where steam-yuzu is a simple bash script that just calls yuzu -f -g "$@"). I managed to evade the issue by changing the curly quotes to normal ones ’ -> ' in the game's path and regenerating the links for Steam.