Hi, genedyne!
Thank you for the suggestion, but unfortunately this is not acceptable for production FW.
My workaround is simple: after AP switches to another channel, Pixel drops WiFi connection in 10-30 seconds and connects to another WiFi. Fortunately, I can detect that another WiFi is used and then I ask the user to connect to ESP AP again. Then communications become working again and the process can be finished.
Since the Setup process is very rare for users and Pixel takes a little share from all Androids - we see this approach feasible.
If interesting, here is my topic on Google Support
https://issuetracker.google.com/issues/121092520, now I created new topic
https://issuetracker.google.com/issues/143505082.
I had faced this issue before , but I didn't dig too deep that time I thought that the issue is in TLS implementations. Now I have proof that this is in WiFi MAC/PHY levels. My supposition is that the issue is related to Pixel specific WiFi Hardware/Driver, because I have other Androids working and hardly to imagine different Android cores for every model.
I am still don't know where is the issue: on Android or ESP, but it's absolutely disappointing to find that you can't rely on standard behavior and have to insert clutches.