IHateMoney.org is a nice self hosted FOSS option, joining groups and organising users is dead easy, but the iOS app sucks.

I personally prefer SettleUp despite it being closed source, I find its functionality a lot better than Splitwise

There are plenty of alternatives to the NUC. MinisForum, StarLabs and System76 out of the top of my head

I have two MinisForum miniPCs and I absolutely love them, I’ve had them on for months at the time without any issues. Before I got them I was looking into the Intel NUCs and they were way too expensive for the specs. Sure, their top of the line NUCs are absolute beasts in a tiny form factor, but their basic entry level stuff is for burning money