Seems raspberry is not supported?
Traceback (most recent call last):
File "/usr/bin/add-apt-repository", line 95, in <module>
sp = SoftwareProperties(options=options)
File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 109, in __init__
self.reload_sourceslist()
File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 599, in reload_sourceslist
self.distro.get_sources(self.sourceslist)
File "/usr/lib/python3/dist-packages/aptsources/distro.py", line 93, in get_sources
(self.id, self.codename))
aptsources.distro.NoDistroTemplateException: Error: could not find a distribution template for Raspbian/buster