Ah ok that’s smart, so you don’t have to mess with installation and still can manage your own CA from the *.domain.tld. I just double-checked, I’m very sure it was on iOS but some years ago. Apparently it’s possible to install custom certs there as well but it’s a little painful

edit: ok I think the general problem on iOS is to install custom certs globally, e.g. to use for the calendar I guess

Personal Certificates can only be installed in Safari.
NO other browsers are supported.

https://kb.mit.edu/confluence/display/mitcontrib/Installing+Root+and+Personal+Certificates+on+iOS

Can you though? I used to do exactly these things and either on Android or iOS I had trouble installing a certificate. Well, in a way it’s not a a big issue anyway, probably it’s smart to go with public domains anyway (even for private resources)