Packing, relative/absolute impossible

so, I’m desperately trying to upload this Blend to Renderstreet. In order of appearance:

  1. IES won’t pack. OK, figured how to integrate the code in scripting area. Not “user friendly”, though.
  2. External libraries are missing. I’m supposed to make all paths relative.
  3. Packing everything into Blend doesn’t work. External libraries are missing.
  4. Making paths relative doesn’t work. 192 out of 401 failed.
  5. The F3-accessible “Pack Blender libraries” command: “Cannot pack absolute file” - loop of poop

I’m suspecting this happens, because these are sitting in cloud files, or are on a different disk than the blend (thus, I can’t make relative paths in Win 10, according to my findings). Either way, this would be stupid.

Is there a workaround/addon that’s not from 2015?

Blender 2.93.4 LTS, Windows 10