I usually end up going to indies for all service but also ask around the Porsche Club who are well regarded and known. There are some indies here in socal that are run by retired master techs. I also take some time to speak to the owner if they’re there and just get a feel for how much they know about Porsche.
Also, some very experienced indie shops can fix things that Porsche won’t like valve bodies, sensors, etc in PDK transmissions. Dealers will whole replace it whole because they don’t want to troubleshoot it, while a good indie can diagnose exactly what parts to replace and save you a fortune.
That isn’t to say there aren’t good Porsche dealer service departments, they pay very well and have amazing benefits so it’s a dream job for a lot of mechanics and they treat it that way. The one local to me actually does vintage restorations and it’s pretty amazing.