Joycontrol is not working with Switch Firmware 12.0.0
You can refer to https://github.com/mart1nro/joycontrol/issues/104
Joycontrol and thus this repo is currently broken with Switch firmware 12.0.0
I was able to get this working by using this fork https://github.com/Poohl/joycontrol. It is an existing pull request into joycontrol so hopefully it gets merged soon (https://github.com/mart1nro/joycontrol/pull/110)
Run Joycontrol on its own and get it to detect and connect to your Switch. After you confirm that fork works for you, run
sudo pip3 install /your/location/to/the/folder/joycontrol
Then run this switch-remoteplay server. This worked for me after some trial and error.
here https://github.com/Poohl/joycontrol/issues/11#issuecomment-920226012