@losses This is something odd. I have been doing a project from scratch, adding folders, creating materials and material functions and nothing happened as described above. I have also switched later to the new Material Layer system and was even hoping to have some crash, but all is doing fine till now and see that I have totally converted the material setup created to the new layering system, with no crash (using 4.20.2).
Are those insta-crash jumping out of the crash-dump screen? Are you able to at least send the crash-dump?