This. Some of my Structural engineering professors have invested so much time in Excel they practically have an instance of their mind in it. Really fancy systems too that could do just about anything they needed. Always impressed me.
For photo storage, I personally use nextcloud for hot access and backup an encrypted copy of all my photos to Wasabi AWS S3 equivalent and Online.net's cold storage under the intensive class. I find it worth it to pay for backing up to those services since I take photos of almost everything and I would hate losing them.
I like to use youtube-dl to automatically download videos from channels I want to follow (subscription feed replacement) and use hooktube to watch YouTube videos without providing Google with data. I haven't found a problem with that till now except for discovering new content (hooktube isn't that good with that, I found), so for that I have a YouTube only account that is pretty much disconnected from me in everyway (even IP address wise through VPN) made with non-real info. I hope that gives a few ideas for media consumption without sacrificing privacy :)
PS: I cannot add links to youtube-dl and hooktube because I'm on my phone, I believe a quick search can provide them.
Not from what I can see in the control panel. I personally use zero-tier to connect my servers on a virtual Ethernet adapter. But you probably want to avoid getting an ipv4 if I'm guessing correctly, so I don't think that would work for you.
I pay Hetzner via PayPal, and I haven't had any fees attached. Online.net however charges a card directly so my bank does charge it as a foreign transaction and adds a percentage.
There's a project called Leela Zero on Guthub which appears to be Alpha Zero without it's neural network weights. I doubt it'll get the proper weights any time soon though.
Your project is a great read!