as it stands, there is no current (precompiled and packaged) mongodb server for Raspberry Pi OS.
Yes, it’s possible to compile the community edition, but then it’s missing systemd control files. And it’s tedious to keep it up to date.
Then there is the Ubuntu version - which has a bad taste on Raspberry Pi OS (which is Debian), but seems to work as of server 4.4, while 5.0 crashs with “illegal instruction”.
Finally, there’s the Docker image, which also doesn’t run in 5.0, but warns:
WARNING: MongoDB 5.0+ requires ARMv8.2-A or higher, and your current system does not appear to implement any of the common features for that! see https://jira.mongodb.org/browse/SERVER-55178 see also https://en.wikichip.org/wiki/arm/armv8#ARMv8_Extensions_and_Processor_Features see also https://github.com/docker-library/mongo/issues/485#issuecomment-970864306
which is more helpful than the “Illegal instruction”, but doesn’t work like that.
So what does the roadmap say?