Either I teach myself to hack NGINX config files so I can move my Nextcloud instance to foo.ddns.net/nc or I teach myself to hack DNS so I can move it to nc.foo.ddns.net. Don't really care much myself which one it is other than that it's the easy way; the main point is to allow me to hang more services off that server. Just kind of my own self-education project that leaves me vulnerable to getting my server pwned.

(Thinking about setting up a Bitwarden instance, a blog, possibly getting a real domain and setting up an email server, that kind of thing.)

I've already got Nextcloud up and working at foo.ddns.net - using subdomains like "nc.foo.ddns.net" is easier (single line change, literally) than moving it to foo.ddns.net/nc, which requires picking apart the config file with a fine tooth comb as near as I can tell.

From the docs I have grokked so far, you can put each subdomain in its own config file, completely separate from the other files, and they won't conflict with each other.

Edited to add - one of the things I loathe about being self-taught through experimentation and just randomly stumbling on to things is that I don't always know the proper terminology, have no idea where to look for things, and have this fear deep down inside that I'm leaving my pants around my ankles.