As long as you can still get to the web recovery UI, make sure to flash OpenWrt using a Windows based browser. Firefox e.g. on Linux will break (seen it with DIR-878 A1 and there's multiple reports on this forum with newer 802.11ac D-Links about the same issue).
It can be a bit finicky. Don't forget to set your client to a static IP in the same subnet as the recovery (see D-Link's instructions for that). And snapshots don't have a web UI indeed but you should still be able to get in over SSH if it managed to boot normally.
That was my original plan rc5 then i had to jump through hoops downgrading ofw etc they never make it easy!
it worries me it is nolonger reachable on its default ip though since flashing opnwrt factory image or now that i think about it openwrt uses 192.168.1.1 and not 0.1 like dlink fw that could possibly be my answer
Have you tried rebooting it e.g. 2-3x?
As it has this internal secondary vendor firmware partion. It may eventually use that partition to turn back to an older factory firmware version.