I use zerotier for that kind of stuff, mostly because it runs native on my router (mikrotik) and is zero config so easy to run on a random mobile device I might have on me.

“If you ever use containers to self-host, do you prefer manual or automatic updates?” “Yes”

I’d say write it for yourself then worry about the cross platform later. You can always go back and rewrite.

That sounds like the kind of stuff we make at $dayjob (that’s for the building trade, where they often have complex spreadsheets and going to an app that calculates everything down to the number of screws for them is a huge benefit).

You could probably still do it with a spreadsheet, just have parts list add/remove fan out into the cutting list and update automatically. I imagine it’d get quite ugly, but doable. If you want to do optimisation (buy 1 5 foot length and cut rather than 2 2 foot lengths, because it’s cheaper, for example) it gets even uglier and at that point a bespoke app becomes more sensible.

zfs-zed, if you haven’t installed it already. It will email you after a scrub, or if there’s a failure etc.