Home Server Advice

Hi, so, I'm looking for some advice.

I currently pay for Microsoft Family (Office + OneDrive). Currently, all spots are taken (6 total). Out of those 6 users, only 2 use Microsoft Office. The 6 of them use the online storage but the biggest user has 300GB occupied out of the 1TB each of the users gets.

Last year, Microsoft increased the price by 15-20%. It was still worth it, but doesn't feel great to get such a price increase. After that, at some point in the year, I started seeing Copilot in OneDrive (Browser - I don't have the app). It's annoying. Every time I click more than 2 items, Copilot asks me if I want all my stuff to be scanned. I really don't.

Anyhow, I imagine with how things are going in the world, Microsoft might increase prices again and, while I'll have to renovate my subscription for another year (February), I'm planning my family's exodus.

The situation is the following:

• My family is split between two countries.
• We want a system just for fileshare/storage (not opposed to adding things like movies or music in the future but it is not a priority).
• I want something simple to use and easy to maintain.
• Important: I want a system in which I can keep a full copy of everything in each country for back up purposes (my brother would maintain a server in one country, I would maintain the other server in the other country).
• My brother is tech savvy but hasn't really looked into Home Servers (he creates applications with google services and stuff). He also doesn't have too much time at the moment.
• The reason I'm the one looking into this is because I'm the weakest link. I can do basic things like install Linux (recent), build a computer, update the motherboard BIOS, some Unreal Engine with C++ but ultimately I haven't dealt with much of this stuff. So, ideally, I'd find something that works for me and my brother would adapt.
• For this project, I can buy a mini pc or one of those old towers at a pc shop (intel 9500, 32gb of RAM, etc.) or anything that's not insanely pricey. Regarding the applications used for the server, I wouldn't mind buying a one time license but I prefer no subscription fees.
• I can read documentation if needed. Just looking for someone to point me in the right direction.

That's the situation. I've lurked this reddit for a bit. I saw some things that looked interesting, like TrueNAS, OpenMediaVault, CasaOS but I don't really know any of them or anything. I do have an old laptop I can experiment with ahead of time.

Anyhow, looking forward to some of the comments.