I’m sure you know the only truly future-proof solution is a text editor, but that aside, I’ve helped my Mum for many years trying to deal with the Ancestry software, which included multiple changes of ownership that I’ve lost track of.
But just recently, she heard about an alternative and once we got it up and running we both like it a lot. It’s called Reunion.
Mum has been doing what I would call traditional genealogy research for decades and she’s really taken to it — she’s in her 80s — and I’ve found it more capable than the Ancestry ones she’s used for years.
It doesn’t integrate with all the modern web stuff, but if you keep your research separate from your recording it’s great.
And in terms of text files, there is the standard GEDCOM format. Most applications will be able to export and import.