We didn’t do anything special except use a non-main branch of the db (because Planetscale has branches and you can’t do schema modifications on the main branch). And we’ve just continued to use that. It’s not for a production site yet, but seems fine at this point. And probably will remain so for our use case (as backing an 11ty-generated site).
The only issue we’ve seen, which we thought was “normal” but maybe is related to Planetscale, is if certain fields are renamed (in particular, to the same name but different capitalization), Strapi can’t make the schema change it needs to be done manually in the db. Not sure if that’s related to Planetscale, but it’s not been a big problem.