Well it doesn’t hurt to write in English, as we are all struggling with in essence the same problem. That FP3 since the recent upgrade to Android 10 looses it’s Wi-Fi. 
I have done as suggested earlier and changed the Wi-Fi channel to anything below 100. Now the STB is unhappy, as it is using 5GHz, too.
I hope FP will soon release an update …
About the same problem here, since last systemupdate yesterday (update 5 Oct.) (not since upgrade Android 10, although?) Sometimes, after reset router and restart FP3, for a little while (up to app. 1-2 minute at the most) wifi-connection. I wouldn’t blame the router but the systemupdate! Please do something about that! In the meantime back to factorysettings? Very annoying!
Mads
I have a very similar problem, not sure if it is exactly the same as described above:
My Fairphone 3+, just have it since some weeks, always disconnects from wifi for 2 or 3 seconds, then reconnects immidiately. This happens around two times per hour.
For some use cases this is not a big deal. But for me this is a huge problem:
Some details: I am using 2.4-GHz networks only. It happens with bluetooth turned off or on. It happens in different networks / with different routers.
Phone was shipped with Android 10 and it happens in all versions / updates since then.
I have contacted the support, but it seems like they have to deal with a lot of bug reports recently and had no time yet the answer.
But if somebody has an idea to fix it: Would be very appreciated, as this bug is driving me mad and makes the phone impossible to use (except regular phone calls).
Just got a fresh FP3+ on December 30th, and the first thing I noticed while playing with it is that the WiFi disconnected all of the sudden and then reconnected. Now on day 12, this seems to be happening several times a day. Makes the phone really hard to use, especially for use cases like video calling.
I’m using Ubiquiti Unifi accesspoints (Lite and LR) and no other WiFi device in my home has this issue.
To all who replied earlier - how is your situation now, any updates?
No updates on my side, the reconnections still happen (OS v66).
Yes, in my case one or two times per hour. Very annoying.
As said in another thread, Fairphone will release a new OS version tomorrow. It is meant to solve issues with phone reboots and brings back calling functionality for some problematic carriers. And I put all my hope in, that this update will also fix the WiFi and some other issues.
Fingers crossed!
I experience also wifi disconnects since updating to Android 10 on my fp3. It seems that the Phone disconnects (and afterwards reconnects) after successful roaming from 2.4 GHz to 5 GHz and vice versa. As a workaround set wifi frequency band to use only 2.4 GHz at fp3’s preferences of the affected network, this makes wifi stable again but results in speed loss.
Android versions 10 and 11 from other brands seem to be also affected - so Fairphone support should escalate this behavior at Google/Android developers side to have the issue fixed for us in the future!
Hello and welcome to the forum.
Good to read, that the workaround is doing OK.
There is an update anounced for tomorrow (see the posting above yours). I guess, it could come later to some users, as the rollout is done by the network providers.
Maybe this issue is solved by that update as well.
Otherwise I would advise, to contact support direct by mail or phone and let them know.
As this is a community forum, there are no support members here, reading all the postings. Therefore it is - unfortunately - not guaranteed (or rather unlikely), that support will take notice of your findings.
Thank you for your response! I don’t think that the problem will be fixed with the next update because a related bug report is already created at Google (https://issuetracker.google.com/issues/168988288) and nobody there mentions that a fix is on the way.
Last time I reported an issue to Fairphone support it took me hours to collect the requested information and at the end the issue was fixed six months later :)) This time where a bug report at Google is already written and a lot of Google Pixel customers are already pissed off, I hope the issue will be fixed at Android and afterwards at Fairphone automatically without my direct intervention. I posted the workaround to help people here until then.
That’s just one possible reason for the reconnects. In my case, I only use 2.4 GHz networks. No roaming between 2.4 GHz and 5 GHz or between different access points. There are just reconnects even when having 100% signal - other devices on the same network have a stable connection all the time.
Not all people can do that because they are affected by the “wifi band switcher becomes invisible”-bug. Same do I. So there is no chance to switch or disable wifi bands 
Let’s all hope for the release of the new OS version! 
My solution at the moment: Turn on Airplane mode for some seconds, turn off, Internet “work” again for a while
Sorry for quoting myself: New update (v0077) did not solve the issue for me.
I must say, I have not noticed this issue any more since the update. Might be simply because I missed the instances where it actually did happen. Would be nice if there were a pre-defined, consistent test we could run on our phones to determine if the problem is there or not. Ideas?
The simple test I am doing:
Establishing a SSH-connection out of Termux from FP3+ to a local server. There is a simple Bash-script running, printing the time every minute. So it is easy to see when the wifi disconnects.
Have been running this on several Android phones. All of them keep the connection, just the FP3+ is disconneting from time to time (usually multiple times per hour).
I reported this to the support with details and screenshots.
But there is no need to do tests like this, as it also happens in regular use, which everyone can do:
In all these use cases I still have the short interruptions of wifi (disconneting and reconnecting again after some seconds).
I use WiFiman from Ubiquiti to identify wifi issues on my phone. It enables to analyze the wifi connection and shows mac address and signal strenght of the accesspoint you are currently connected to.
Thanks for the suggestion - I have a lot of Ubiquiti equipment here but did not have this tool installed yet. Just not sure if it can run in the background and perform a connectivity stability check over a longer period?
No, checking the connection for a longer period of time isn’t possible yet. But in my case disconnects happend every time I roamed succesful between accesspoints and/or different band (2.4 GHz / 5 GHz) and vice versa - to identify such problem the app was very helpful.
Hi All,
I had before similar problems with continually disconnecting wifi. And changing frequency 4,2/5 Ghz. For me the problem was solved by setting the prefered freq band to 4,2Ghz (in the properties > Advanced of the connected network).
However…, since the last Android update (FP3+, Android version 11, date 5 april 2022) the problems are back again. But now the option for setting the prefered freq is missing…!?? 
I would appreciate some help
Hi and welcome to the forum.
At home you can create different SSIDs on the router for 2.4 (not 4.2 )and 5
You can also disable the 5Ghz if you like
On the phone you can select either or both of the SSIDs to be connected automatrically or not.
Personnaly I have 5GHz on auto and 2.4GHz not so, so if I want 2.4 I have to slecect it manualy.
Tips to fix-
Unplug the router and modem’s power cords from the power outlet for 15 seconds.
Plug the power cords back in.
Check that all cords and cables are secure at both ends.
Wait a few minutes, until the lights on the modem and router are working right.
Greeting,
Rachel Gomez