It turned out to be surprisingly annoying to do this on Debian due to the MongoDB requirement. I forget the exact difficulties but I ended up having to punt and run the container from linuxserver.io.
Ahhh that's it, I think. It was on ODROID H3+, these run on pentium silver N6005 which don't support AVX, which means that "newer" MongoDB won't work without jumping through hoops to compile from source. I just ssh'd into the vm where I run it and it seems like I DID eventually get it working - with mongodb 4.4.x but it's not supported anymore :(
