Qualcomm supports the QCM6490 in the Fairphone 5 for 5 years, until 2028. The “eight to ten” years Fairphone is promising is more like how they’ve been supporting their previous phones (as well as they can, but incompletely).
5 years is still much better than the typical 3 though, and probably enough for most people. That level of support matches Apple (minimum 5 years) and Microsoft (minimum 5 years of mainstream support).
The other problem Fairphone consistently has is that they do release security patches, but they do so months to sometimes even years late. Big problem with the Fairphone 4.
On the bright side, Fairphone might’ve figured out how to use proper signing keys this time around: