Yes, I just flashed the Installable zip.
It’s not your fault it isn’t working with Windows, the dependencies are just a big mess.
Interesing, the ota update still fails, after flashing the stock rom (A.105). Because of the unlocked bootloader? I’m downloading the flashable A.110 now and try to flash it.
installing TWRP will indeed prevent you from using the OTA. When you uninstall Magisk, it will not restore the original boot.img but the modified one. Thus you must not install TWRP if you want to go this route.
I’d expect that removing system applications modifies the system partition, thus OTA will fail for that reason too.
I did the OTA with bootloader unlocked, so that alone definitely doesn’t have any effect. Any modifications to any of the following partitions (it’s enough to briefly mount one of them read/write, even without changes) will break the OTA update:
aboot
boot
cmnlib64
cmnlib
devcfg
dsp
dtbo
keymaster
lksecapp
mdtp
modem
product
rpm
sbl1
system
tz
vbmeta
vendor
The FP OTA so far are always differential updates, which means it contains binary diffs along with checksums of “before” and “after” - applying the diffs (patching) would fail if anything is different or worse - lead to a corrupted filesystem, so the update engine compares the checksums for each of those partitions first, and aborts the update if there is a mismatch to avoid bricking the phone (so this check isn’t just to make our lives difficult, the check actually makes sense 
)
This means, if you have installed magisk, TWRP, or both, rooted the phone, did any changes to system, or even just mounted it within TWRP once, you need to first go back to the original one OR apply the update yourself.
You can “simulate” an OTA by flashing the new image to the currently inactive slot, then attempt to boot from it. (possibly after also installing TWRP/magick/etc… in the freshly flashed slot as well) If that booting fails, the phone will do what it does in OTA’s, too, it will automatically revert back to the old slot, and you can try again, but you still have a working phone and access to all your data.
Thank you for the detailed explanation.
So that means, that deleting system apps isn’t an option when wanting to do ota updates in the future. Though disabling works.
What puzzled me was, that after flashing the A.105 Stock the OTA update still failed. I think it would have been necessary to do a factory reset/wipe in TWRP.
No, the A.105 shared online accidentially contained an altered partition which made OTAs impossible.
the first shared full image contained a corrupted dsp partition. you need to find the latest links and redownload. I would suggest installing the A.0110 full image right away.
Thank you, I though the A.0105 was updated with the new dsp partition in the meantime. I will try that now.
It’s not possible to boot the A.0110 at the moment. It freezes while booting, like described in the TWRP installable stock firmware thread.
its now possible with a little workaround.
you need: Fairphone_FP3_8901.2.A.0110.20200109_01092024_user_release-key.zip
and twrp-3.3.1-0_k4y0z-20200131-01-fp3.img
check the slot with fastboot getvar all (it should be b)
fastboot flash vbmeta vbmeta.img
fastboot flash sbl1 sbl1.img
twrp does not flash these 2 partitions at the moment
reboot
There will probably be a new TWRP-release today, to fix that once and for all.
It’s always nice when stuff works out, but depending on what exactly users did with their phone in this early stage of experimenting results might differ (I found out the hard way), so we should be careful for now generalising like that, I think.
Let’s hope the next TWRP will make things easier.
What if the slot with the working OS is slot B?
Why should it be B in every case?
thats what worked for me … . slot b is a good slot so far 
might be good to install and flash it to both slots.
You should always make sure the slot you aren’t flashing to, has a working fastboot.
I will also add a disclaimer for TWRP, since the full-stock images also update sbl1 and aboot (fastboot).
It’s never a good idea to flash the full stock to both slots without testing you can actually boot (at least to fastboot)
at wich partition is fastboot located at? i think it sits at a different chip or so.
The bootloader is in the aboot partition.
fastboot is impelmented in aboot.
For fastboot to be working, at least sbl1 and aboot must be good.
For you. If I understood this A/B concept correctly, it could be slot A for anybody else depending on e.g. the number of slot switches by OTA updates in the past.
I guess we’ll just refer users ruining their currently active and working slot B to you 
.
Or perhaps to this here beforehand … A/B (seamless) system updates | Android Open Source Project
good to know
But if they are good in the stockrom and in the updates there should be no problem to flash both slots.
(wich they are as far as i can see)
I repeat NEVER INSTALL FULL STOCK TO BOTH SLOTS WITHOUT TESTING ONE FIRST!
i try to wrap my head around this concept. I had rooted phones before. The fp3 is the first with this A/B thingy.
Why cant android not be as easy as any other linux? Phonemanufacturers and Google are f-ing cancer. Its always shitty blackbox-debugging. Openssourcewannabes with locked and crippled hardware and systems. Like Raspberry pi. yeeha open hardware with locked gpu… very nice
.