Hey Stefan,
Thank you for your question. As said in one of the topics you linked to: at Fairphone we are very impressed by the work of the community and we believe that their work is a huge contribution to the longevity of the Fairphone 2. Successful alternative OS’s for the FP2 will enable users to keep the phone longer and prevent ewaste.
That said, there are currently no plans to support LineageOS officially. The team has their hands full supporting the existing two OS’s and has no resources to support another one. Let alone the required pressure it would put on the legal, product, communications, marketing and support team if Fairphone start supporting a third OS…
But to explain a little further: the Fairphone ships with Android with Google services; Fairphone OS. If you want to sell many phones in order to achieve impact in the supply chain, there is currently no other option then to use standard Android. The majority of people expect a standard OS that works out of the box with the apps they use and need.
If we look at the number of people that currently use alternative OS’s on their FP2 it shows that only 5% changes the default OS to something else (Fairphone Open, LingeageOS, Sailfish or Ubuntu).
Making Fairphone Open is a small effort for us as it is very similar to Fairphone OS and puts little pressure on the teams capacities. Supporting a whole new OS, like LineageOS, is really no option.