Debian 8: (jessie): http://repos.rcn-ee.com/debian/

deb [arch=armhf] http://repos.rcn-ee.com/debian/ jessie main
#deb-src [arch=armhf] http://repos.rcn-ee.com/debian/ jessie main

Debian 9: (stretch): http://repos.rcn-ee.com/debian/

deb [arch=armhf] http://repos.rcn-ee.com/debian/ stretch main
#deb-src [arch=armhf] http://repos.rcn-ee.com/debian/ stretch main

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

Ubuntu 16.04 lts: (xenial): http://repos.rcn-ee.com/ubuntu/

deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ xenial main
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ xenial main

Ubuntu 17.04: (zesty): http://repos.rcn-ee.com/ubuntu/

deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ zesty main
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ zesty main

Ubuntu 17.10: (artful): http://repos.rcn-ee.com/ubuntu/

deb [arch=armhf] http://repos.rcn-ee.com/ubuntu/ artful main
#deb-src [arch=armhf] http://repos.rcn-ee.com/ubuntu/ artful main

keyring:

sudo apt-get install rcn-ee-archive-keyring