The article I just linked says they’re extending support to 7 years: Out to 2026 for their 2019 model, the Fairphone 3. The article also links to an older article talking about how the Fairphone 2 ended up with 7 years.
I’m in the US so the Fairphone was never really a consideration for me, but if it’s available whenever I need my next phone I’ll definitely look into it. It’s pretty annoying to be using Google’s own phone, and still only have access to 3 years of OS updates.