This is just because you are used to windows and it's issues. I've been using Linux for 15 years now and I think this about Windows. It works great, in particular for some specific applications, but it is a pain to use. It is slow, lacks customisation and you always have to install drivers for any device you want to use. Plus those updates are really annoying when you don't boot Windows for a long time. You can't use your computer while they are installed and of you have a lot of them it can take a really long time. I'll never switch to Windows!
If you run immich with docker, you can choose any drive/folder for your photos by mounting it at the right location inside the docker container.
However, I would strongly suggest that you also use some other kind of backup beside rest. I personally like restic combined with Backblaze B2, but there are many other good solutions for this.
A good alternative to carrying 2 tubes is to have some patches with you. I can understand that they may be too much work for fixing the first flat but they could save you from the next X flats for almost no extra weight/room.
My first power outage was a very bad experience since I was absolutely not prepared for it.
I have no ups since the grid is very stable in here (it's been the one and only outage in 5 years). The outage was short but I had forgot to activate the option in the BIOS of my server to power on when plugged in. So my server stayed shut down after electricity was restored. Of course, I happened to be away for the whole week when this happened with no way to access my server physically.
This is the event that made me learn about and start using a KVM that I can use remotely.