Figma isn't a collaborative platform beyond your own project, it isn't a GitHub, it's for propertiary design of your products.
The only thing Penpot has to do is "disrupt" the pricing equation and some businesses will pick it up to save some bucks, heck to even retain independent control.
I think the main blockers are the pain of re-learning the software, and migrating things over. Lots of designers have down this already in the last few years from sketch.
It's like software frameworks where young designers want to learn the most popular, coolest tool to help find a job, and companies want to use the most popular, coolest tool to help with hiring.
I don't think it being self-hosted changes this for better or worse, but they still have a tough task ahead to get a critical-mass switching.
The only thing Penpot has to do is "disrupt" the pricing equation and some businesses will pick it up to save some bucks, heck to even retain independent control.