I have the same issue here. It looks like all strictly confined, graphical applications I have installed as snaps have stopped working.
I can reproduce the issues above for Discord and Telegram. In addition to that:
$ snap run firefox
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
Error: cannot open display: :0
$ snap run chromium
/snap/chromium/367/bin/desktop-launch: line 23: /home/tim/.config/user-dirs.dirs: Permission denied
Failed to move to new namespace: PID namespaces supported, Network namespace supported, but failed: errno = Operation not permitted
fish: “snap run chromium” terminated by signal SIGTRAP (Trace or breakpoint trap)
$ snap run ohmygiraffe
xcb_connection_has_error() returned true
shm_open() failed: Permission denied
AL lib: (WW) alc_initconfig: Failed to initialize backend "pulse"
ALSA lib conf.c:3750:(snd_config_update_r) Cannot access file /usr/share/alsa/alsa.conf
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM default
AL lib: (EE) ALCplaybackAlsa_open: Could not open playback device 'default': No such file or directory
Could not open device.
/snap/ohmygiraffe/3/bin/launch_omg: line 59: 13584 Segmentation fault (core dumped) $SNAP/usr/bin/love $SNAP/oh-my-giraffe.love