@Lubomir 

it looks like this choice is only in stand alone.
but before you go stand alone you should test this beta version, the version you have is very old

https://community.tp-link.com/en/business/forum/topic/604386

  @MR.S 
Thanks a lot for the pointing to the newest firmware. Already installed it, going to test it for few days. Will share results there later.

  @Lubomir 

I installed Omadacontroller 5.11.x beta and it looks like that function has been reintroduced again :-) so in a few months it will probably also come to OC200

  @MR.S 
Can I download it somwhere and try?
The latest firmware for EAP620HD looks like didn't help for my issues - still Samsung Galaxy S22 has issues with internet, however it's strange that it's not permanent issues. Also my Windows 11 laptop supporting WiFi6 started to have the same issues. What's interesting that all devices which has WiFi6 issues started to work Ok if I connect them to WiFi5 router. So issues only when I'm using Omada APs.
 

  @Lubomir 

you can find it here, it is only for windows

https://community.tp-link.com/en/business/forum/topic/612908

MR.S wrote

it is only for windows

  @MR.S 
That's bad... I thought exists version for OC200. However thank you anyway!

Posting some results:

So upgrading of EAP firmware to the named Beta version didn't help. Moreover the latest version which is 1.1.0 is the most problematic, so I downgraded back to 1.0.6.
Didn't try the beta version of controller as far as I don't have PC server (either Windows or Linux). So I'm sill waiting for OC200 upgrade with possibility to choose radio mode again.

For now I downgraded EAPs to be used in standalone mode with AX mode switched off, though all other Omada hardware is running in controller mode.
Actually this helped not too much. Still Samsung S22 had issues with interrupted internet over WiFi (some sites and applications reported lost connection to the internet, Instagram videos are stuck to load, the same for Youtube). Also some issues were with Galaxy Tab S8 with connection to the internet (some games reported that connection is lost to the internet but in fact WiFi connection was stable). However other devices connected to the same WiFi AP were fine.

I think the issue is somewhere in between Android 13 on Samsung (I have issues only with Samsung devices with Android 13) and TP Link access points firmware or hardware. I also tried the same Samsung devices with other producers routers (even no-name Chinese) - no issues at all (though it was only in WiFi4-5 modes and not mesh ones).

However I switched off some advanced settings on the TP-Link EAPs (like band steering, power save, load balancing, airtime fairness and OFDMA) and now looks like Samsung devices are much more stable but I have now all WiFi devices running without good speed and no mesh anymore. Some issues still happen but much more rare than before. Means I spend a lot of money by upgrading to Omada for nothing - still don't have good coverage and still have roaming issues with my WiFi devices and still need to configure every AP manually.

I plan that I can try again EAP in controller mode but without advanced WiFi features turned on. And check if there were those features concluding those troubles with connection to the Internet for Samsung devices in WiFi6 mode or not.

Also forgot to mention that after I switched to standalone mode for EAPs - internet become visibly more fast even with using less speedy protocols. So probably the issue also somewhere in Omada system, e.g. in communications of OC200 with EAPs or somewhere else.