I have installed LineageOS 14.1 today following the steps in the first post and so far I am quite impressed. Thanks to all who made this happen!
Since I used an encrypted data partition on FP Open I had to do an additional step: A factory reset and wiping the data partition wasn’t sufficient. Only after formatting the data partition I was able to boot into the new system. @snevas Maybe it makes sense to add this info to the first post?
Changed it 
thanks!
@snevas I would format the data partition only in case the data partition was encrypted before (because the current LineageOS version is not able to decrypt the data partition). In all other cases a factory reset may be sufficient (and has the advantage that the data on that partition will not be deleted).
I have installed the latest build OTA. But the automatic (daily) check of the updater notifies me of a new version, that is already installed.
Do you have the same behaviour?
I get the same behaviour on official LineageOS devices like Moto G and Moto E (I’m still running FP Open in my FP2).
I moved this topic to #software:dev because it attracted issues that should go to
Please discuss everything that is not related to OTA updates there.
Amazing job, thanks a lot 
If there are new developments regarding OTA updates, you can contact me and I will open the topic again. Otherwise the topic will open automatically by the start of next week.
I have fixed the issue with the new update available, I needed to change the timestamp of the zips to the builddate for it to not register as a new update. I fixed this for the last release and every upcoming one that will be built.
I have a question regarding porting Lineage to FP (I want to try the OTA-Method coming from FP Open. Why do I have to update TWRP? Can’t I just wipe and flash using the existing TWRP? As I have root, can I use the app, or do I have to flash aswell?
The patch for TWRP is only useful for OTA updates, if you don’t use that patched version, the updater will be rebooting to recovery, but not applying the update automatically. It should hopefully be soon™ be integrated into the normal build at twrp.me . EDIT: It’s actually already merged but not integrated in a build. So the next release of TWRP should include it
I just installed Lineage! Thanks to all who realised this. How:
Flashed TWRP .img through TWPR and said reboot to recovery
Noticed that TWRP hat noch updated. Re-flashed TWRP.img and just shut down system. Rebooted into TWRP directly - TWRP hat updated.
Then flashed lineage.zip.
Now I just have to “install” the FP ringtone.
OTA Update has been worked as described (coming from Lineage OS). Thanks!!
The new OTA went smooth without errors or hiccups - as always. Haven’t testet fm radio yet and don’t use encryption at the moment, but anyway, this is amazing.
Many thanks to @chrmhoffmann, @snevas, @z3ntu and the whole crew.
When I download the OTA update I often get a ‘Verification failed’ error and the update fails. A reboot usually resolves the issue and the update is installed without problems.
Is this a known issue? Am I doing something wrong?
Huge thanks again to all the people who brought this awesome OS to the Fairphone 
This is just a hickup in the download. It checks a checksum before installation and doesn’t install it when the download is corrupt.
Redownloading normally solves this problem.