Debian 10: (buster): http://repos.rcn-ee.com/debian/
deb [arch=armhf] http://repos.rcn-ee.com/debian/ buster main
#deb-src [arch=armhf] http://repos.rcn-ee.com/debian/ buster main
Debian 11: (bullseye): http://repos.rcn-ee.com/debian/
deb [arch=armhf] http://repos.rcn-ee.com/debian/ bullseye main
#deb-src [arch=armhf] http://repos.rcn-ee.com/debian/ bullseye main
Ubuntu 18.04 lts: (bionic): http://repos.rcn-ee.com/ubuntu/
deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ bionic main
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ bionic main
Ubuntu 20.04 lts: (focal): http://repos.rcn-ee.com/ubuntu/
deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ focal main
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ focal main
keyring:
apt-key adv --keyserver keyserver.ubuntu.com --recv-key D284E608A4C46402