Not sure if they will ever add relay management. Primal uses a caching system to retrieve notes and have them ready to serve up to users instantly. Not sure what relay list it draws from, but hopefully it's casting a wide net. I think they are focusing on simplifying things like that for normies to provide a less complicated UX.

Unfortunately my UX with Primal for Android has been pretty garbage. It only loads a handful of recent notes when I have it open and there no way to get it to load anything in between those and the handful it loaded the last time I opened it. If I haven't opened primal for 8 hours I don't get to see anything posted ~1-8 hours ago.