A web search comes up with a lot of users like me who keep their OS on a SSD, and keep their content (minecraft) on a drive that is mapped as a folder.

The issue is outlined pretty clearly here:
[#https://bugs.mojang.com/browse/MCL-5385]

The "solution" is not clear, and I think the launcher should be repaired rather than requiring technical solutions by users. We haven't been able to play minecraft since the launcher updated. Tons of other games work fine this way, including games using launchers like Steam and Origin.

If nobody wants to fix the launcher, please instead provide instructions for us.

--Thanks,
long-time minecraft family