Best way to keep my German number active while moving abroad?

Hey everyone,
I’m moving to another EU country soon and I need to cancel my current SIM contract with sim.de. I want to keep my German number though, mainly to receive SMS and calls, since I might move back to Germany in the future.
I don’t want to pay much per month, ideally nothing or just a very small amount. I was thinking maybe porting the number to a prepaid provider could work better.
Has anyone done this before? Which provider or option worked best for you?