I would like take the opportunity with my TV box to learn to walk on my own legs and build Armbian from source. I followed the Armbian build documentation, cloned the Armbian build repo, ran the compile script with the options below, chose the Odroid-C4 as the target board in menuconfig, and let the script and gcc crunch their way to the end. Support a311d, s922x,. Armbian is licensed under GPL2, whereas both Raspberry Pi OS and Debian GNU/Linux use a mix of licenses, including GPL and others. The Raspberry Pi OS image “with recommended software” contains several “free-to-use” commercial software packages, most of which are limited demo versions...
Obviously some configurations are in a different place here and there, but it's basically the same. I don't think you can run armel. The armhf packages probably will work, but then it's the same issue with using packages from the Debian repository in Ubuntu. You should use the Ubuntu packages which are basically the same source, just repackaged..
Compare raspap-webgui vs WiFiMeshRaspberryPi and see what are their differences. raspap-webgui Simple wireless AP setup & management for Debian-based devices (by RaspAP).
At the time of this writing A1 and A2 cards are only widely available from SanDisk. Armbian recommends A1 rated SD-Cards only now (A2 rated cards need yet lacking driver support and therefore show lower overall and especially random IO performance).For example: In case you chose an SD card that was already in use before please consider resetting it back to 'factory.