It's a photo album? I kept hearing about it. I've been using a combo of just plain files, and sometimes nextcloud. Immich sounds like something to look into.
Is this for quantum resistance? The certificates would be pretty large and they don't give a key agreement scheme, just signatures. They are clever but to deploy them on internet scale would take a lot of software changes in everything.
Only one person has solved one so far, and he turned down the $1 million. Go figure.
For programming, try rubyquiz.com. It's supposed to be Ruby exercises and some of the problems are Ruby specific, but lots can be done in any language you want.
I don't know of an all-in-one-place guide but there's not a whole lot to it. Just look up how to do each of the parts you mentioned. I'd say that buying a domain and using LetsEncrypt is not really in the self-hosting spirit (i.e. you should run your own DNS and CA) but it's up to you. Running a serious CA with real security is quite hard, but for your purposes you can just do whatever. There are various programs or scripts for it. I still use CA.pl from the openssl distro, but that's very old school and people here hate it. Anyway, you will do a little head scratching to get everything working right, but it will be educational, so you'll get something out of it in its own right.
You don't like Festivus?