but your appliactio seems to be able to run as root so you should not need to do anything, if your app starts as a daemon it should a) be running as root and thus have full access to the serial device (like jamie said above) … or if you run the app as a user and the user is in the dialout group it should have full access (same should go for running the app via sudo)
Thanks @jdstrand. I’m juggling a few things at the moment and unfortunately just haven’t had the time to try out the suggestions here. I appreciate all the help from everyone though - I would be totally lost in this otherwise! I’ll give y’all a shout once I have time to devote to debugging snap permissions again.