Just a potentially-dumb question - let’s say you sell your Mini for 500 euro, and you buy a ThinkCentre Tiny, are you going to get anything even close to comparable specs in the ThinkCentre? I would think your 2018 Mini would likely have a comparable-or-better CPU spec, and more RAM - both of which will be helpful if you’re running VMs and Docker containers.
Assuming that your time has a value greater than $0, it might make more sense to just leave the VMs in place on the Mini (where they’re presumably already running and stable) and just migrate your other data to the new computer.