Up at the top, click/tap settings, dark mode option is in drop down.
I believe he is more showing that he has push notifications working for Memmy.
Awesome, I’m glad you we were able to get it solved and it get everything back working.
I forgot you will also need tty access, so you'll also need to do:
sudo usermod -a -G tty $USER
After that you will need to relogin in order for the changes to take effect. I'd say just to reboot so you know everything is reloaded with:
sudo reboot now
These are all of course assumptions based on your mentioning permissions, and without any logs to verify. If you decide to go with the nuclear option and redo the OS and setup I'd recommend looking at using https://github.com/th33xitus/kiauh. It will allow you to setup Mainsail, but also you can try other front end options as well. Just something to consider if you decide not to continue troubleshooting and opt to start over.
Since you mention permissions/access denied, have you given your user permissions to use serial? You can do this with:
sudo usermod -a -G dialout $USER
What is the output of:
ls -al /dev/serial/by-id/*
What hardware are you using for hosting klipper and mainsail? Are you using a pi and mainsail os or a pi with raspberry pi os and kiauh to setup klipper and mainsail? Could you post your klippy.log?
Original dev stepped down and transferred the app to the remaining devs. See his post from5 hours ago.