OS for selfhoster. Here’s a video by Dev.
Source-avaliable, but not FOSS. You can’t take anything with the PolyForm license and use it for commercial purposes. Seems like using umbrelOS to set up companies with self-hosted applications might technically be against the terms of the license. Or even using the self-hosted applications for your own personal use and making money from any of them in some way may also be against the terms.