In the past I’ve opted for Armbian on non Pi hardware, still running 16.04 on my OrangePi 2E+ (my headless transmission-daemon torrent server) - it just “works” and has been for 3 or more years, no fuss… rock solid… installed on eMMC - torrents go to an NFS share on my NAS.
I might check out DietPi again one of these days seeings how they now have a 64 bit version for the Pi3 / 4 (last time I looked they still only did 32 bit).