Here is a simple trick: do accept plenty of open source contributions as-is, without any kind of copyright assignment nor requiring to sign anything that grants power to relicense.

There you go, guaranteed community ownership of the code, best face and "good will" as promised by choosing a FOSS license to begin with, and future rug pulls averted.

Seeing it from the other side of the fence: if you see that all contributors are required to cede controlling power into a single hand (except certain Foundations, yadda yadda), it's not proper Open Source in spirit, only in form; and closeups are just a change of mind away.