You can definitely go back to the original OS. Here is the manual:
https://support.fairphone.com/hc/en-us/articles/4405858261777-FP4-Install-Fairphone-OS-offline
I only recommend not closing the bootloader after reinstalling FairphoneOS as this could result in a bricked device (It can be fixed only by Fairphone for approx. 30€)
But only with an unlocked bootloader.
At least this is not fully tested after version 20220405 is installed (changed to user-settable avb key)
Yes, that’s what I said: Dont’ lock the bootloader until this issue is resolved.
Then you should be fine 
Also that should be just a temporary issue, I’m sure FP will work on this to get this fixed. So there is and will be a way back to FPOS
The flag that controls the ability to unlock the bootloader is persistent across reboots and factory data resets, but not across flashes. Therefore it should be safe, if you want to relock the bootloader, to flash FPOS, request a new unlock code and enter it, and only then lock the device.
The device will perform a factory data reset, but not touch the flag. If your device breaks now, you should be able to unlock the bootloader again.
Never mind, you cannot set the flag if the device is already unlocked…
If the above description is correct you would not be able to use/enter the new code, or?
If that is the case I stand corrected, seems stupid though
Many thanks for answering importend questions.
New:
Matrix Room
iodéOS Beta Testers and Community
No one can guarantee that, but the chances are very good. 
Today a detailed review (in German) has been published:
There is more interesting news:
We are pleased to announce iodé is now available in German!
We have recently welcomed a new team member Oliver from Leipzig who will be helping you get your hands on your iodé phone you can get with 50€ off by using the coupon willkommen (available until the 31th May) on your next order !
We have made available a new documentation on how iodé’s ‘degoogled’ Operating System (iodéOS) protects your personal data.
iodeOS.pdf (2,6 MB)
This is the test phase, but will it be possible to OTA-update if the final release is available?
Yes, it only depends in the OTA updater you are using.
Betas have their own updater
Hi there,
New TESTING version of iodéOS, here is iodéOS 3.0, based on Android 12 
It’s avaliable here and here are the instructions 
Neither me or iodéOS are responsible for bricked devices, only do that if you know what you’re doing
[read EDIT 3 first] Please also note that the avb keys were made for iodéOS 2.4, I don’t know for the moment if they are compatible with iodéOS 3.0. I haven’t tested it, as I keep my bootloader unlocked for now. You’ll be updated in the next future (you can also join the Matrix (#iodeOS:matrix.org) or Telegram (just search iodéOS) beta group).
EDIT : Bluetooth audio not working for the moment
EDIT 2 : Bluetooth may work with a workaround, in Developers options, enable the “Deactivate A2DP hardware offload” option. Not 100% guaranteed, worked for @AlphaElwedritsch, may cause another issue with battery consumption, I’m gonna ask for more details 
EDIT 3 : avb keys seems to be usable with iodéOS 2.4 latest builds and iodéOS 3.0 too
Here are some screenshots of it :
Hope you’ll enjoy
First bug found :
For a non-jack phone, that’s a bit anoying, I hope a fix could be found in the near futureKeep in mind that this is a testing version
I would say it’s a first testing version
avb_key ist the same as for iode 2.4 and can be used, too. It will be (never) changed again.
Same issues as in all other custom A12L based ROMs, because they are all on same LOS tree
The bluetooth issues will be fixed in next calyxOS build and will be upstreamed to LOS tree.
Therefore it is only a question of time until it will be availabe on any LOS-based custom ROM and also in iodéOS
iodé is now, the second A12L based security and privacy based custom ROM.
(OK, just for correctness, also LeOS, but it is a GSI Image)
