I have a Fairphone 3, and I like it. Only 3 years so far, but doesn't feel lacking to me yet - it runs just fine. However I don't use it for anything hardware intensive like games, and of course it doesn't have the latest gimmicks like 5G.
As far as I know the company is actually employing people to add support of this phone to new versions of Android - and this involves actual work essentially because hardware manufacturers tend to work on shorter cycles and by now they moved on. To me this is reassuring, although 10 years is really optimistic I'd say.
And the price was really not low - at the time I was buying this, a Motorola with more-less the same chipset was maybe 2/3 of the price, maybe 1/2 of you'd be buying open box. Of course non removable battery, different cameras, etc.