The issue I've found involves flatpak sandboxing preventing the creation of the discord-ipc-0 ipc service which in turn prevents other applications from communicating with Vesktop's built-in arRPC service.
If you're unsure whether you have this issue, check the directory stored in your $XDG_RUNTIME_DIR environment variable for the discord-ipc-0 service file using the command below:
ls -lah $XDG_RUNTIME_DIR | grep 'discord-ipc-0'