Vendor Name: Fairphone
Device Name: Fairphone 3
Device CodeName: FP3 (+)
Version existing previously: e-2.6.3-t-20241219455848-community-FP3
Device: Not rooted
Did the Upgrade as explained by @piero at this link by sideloading (dirty Upgrade).
Up to now, no problems detected. ‘U’ seems to be more stable.
Many thanks to the Team for your good Work.