Cannot open minimserver

[HardBop]

OK, starting to make a bit more sense now...albeit more complicated than I'd hoped! I assume Plex offers a cross-platform option, hence not realising I needed a UPnP control point/renderer? As I understand the terminology, I guess I'm using either my Ipad or Android smart phone as the control point from Plex? I then use Chromecast Audio to "cast" the music to my hi-fi using a standalone DAC.
Grateful if you could therefore provide further advice if possible. For example, am I right in believing than Bubble UPNP only works for android and therefore could not be used via IOS?
Overall, it does sound more involved than I first thought, but I'm happy to pursue, particularly if Minimserver offers better tagging facilities than Plex.
Thanks.