Community Supported Chip. Armbian does not do active development for this board nor does it assist if users run into issues. Depending on kernel branch it might or might not receive updates here and there but they are untested and if they break something, bad luck. Enhancements from the community via PR surely will be accepted.
You can also volunteer to take over maintainership for your board: https://forum.armbian.com/topic/19172-do-you-like-to-see-your-favorite-board-supported/#comment-130484
Maybe Debian simply ended support for Stretch? Which is now old-old-stable?
