[LinuxBender]

Also GrapheneOS [1] but hardware options are limited. LineageOS [2] and its fork /e/ [3] appear to have some more hardware support.

How many years will a phone running these be usable on average?

[1] - https://grapheneos.org/faq#device-support

[2] - https://wiki.lineageos.org/devices/

[3] - https://e.foundation/