After the latest Android 15 version FP4.QREL.15.16.1 with Magisk root, WiFi disappeared. After flashing the same version again (FP4.QREL.15.16.1), the system would no longer boot—it got stuck on “HI”. Because of that, I started looking for which system versions could still boot.
Android 11 got stuck, Android 12 also got stuck. Only Android 13 (FP4.TP31.C.0143) successfully booted. It felt like a “blessing”, because the system finally started working again.
However, there was no connectivity: Bluetooth worked, the MAC address was visible, and the SIM card was detected when inserted. WiFi turns on, but every ~10 seconds it disappears and comes back again. It seems like the network module is constantly “waking up and going back to sleep”.
How can I fix the WiFi issue? I’m praying for help.
Welcome to the community 
Disappearing WiFi when it comes to rooting usual means you’ve flashed/booted a boot.img that’s not matching the current system version, older versions will often boot fine, but you’ll get sound/WiFi/etc. issues.
What happens if you flash an unmodified (unrooted) boot.img for FP4.QREL.15.16.1, does that restore WiFi functionality? 
What I did when WiFi disappeared:
After reinstalling Android with a clean boot.img, OS 15 would no longer boot.
fastboot -w
I flashed FP4.QREL.15.16.1 again, same issue — it got stuck at “HI”.
I flashed Android 11 — it gets stuck.
I flashed Android 12 — it gets stuck.
Android 13 works, but WiFi is stuck again and won’t turn on.
The problem started after I booted an older boot.img with Magisk. It was my mistake, and I guess Gemini is also to blame — I sent it a screenshot showing the Android version and it told me “THIS IS DEFINITELY THE RIGHT ONE :D” but turns out it wasn’t 
So yeah, it was my fault
The photos freeze immediately and stop loading. Android 11, 12, 15.
Android 13 works.
It’s not entirely clear to me if your attempts so far have been just flashing those boot.imgs or if you reflashed the whole system to stock at some point, the screenshots seem to indicate you did the latter
Yeah, I’ve seen that happen before, in some cases that will modify the system in a way that’s only really fixable by a complete reinstall.
I wouldn’t try to get Android 12 running, reflash the latest factory images, pay close attention to any errors the install script might throw at you, and for good measure please post the output of fastboot oem device-info.
(Don’t forget to backup the phone beforehand of course)
That should usually overwrite any of the partitions that might have been modified, unless we’re dealing with a Ubuntu Touch situation here, but that seems unlikely.
After the incident, it was attempted to reinstall from Android 15 down to Android 11 using each downloaded ZIP file, extracting it, and using flash_fp4_factory.
The newest Android 15 version freezes after rebooting, as I already wrote above.
Only Android 13 works, but Wi-Fi is not detected.
I installed the latest version: lineage-23.2-20260506-nightly-FP4.
Wi-Fi is still not working. After inserting a SIM card, Wi-Fi briefly comes back, but disconnects every 10 seconds. After restarting the phone, Wi-Fi completely disappears again.
USB-C file transfer from the computer also does not work, and Windows 10 Device Manager no longer detects the device drivers at all. However, Bluetooth still works and the MAC address is visible.
I think the Wi-Fi/network firmware or chip may need to be reflashed. If the network chip was completely dead, Bluetooth and the MAC address probably would not work or appear.
How can this problem be fixed?
Hmm, that could be a hardware issues, but might as well still be a driver issue, hard to tell. Since it persists across several OS versions I’m leaning towards hardware issue.
I’m not familiar with how the antennas connect to the WiFi module, someone else will have to help you here, maybe that could be an issue
It depends, if those aren’t on the same component they can still be unaffected, I don’t know how integrated they are on the SOC. The MAC address is baked in / gets created randomly (in privacy mode), so a MAC address existing doesn’t really tell you much.
I’d check the antennas, try the phone in other WiFi networks (if you haven’t already), and if that doesn’t help it’s time to contactsupport
The situation is that it’s unfixable on the software side under home conditions. The solution is the Fairphone 4 service center. Thanks to everyone who helped! ;))))) 