@Alam0786 

Do you link these APs to different routers.Also, do you verify if the SSIDs are identical in other devices.As far as I know, some devices may display two identical SSIDs due to different bands.That is really scarce.Most devices are unable to achieve this.Additionally, if the APs are connected to different routers and broadcast the same SSID, the phone may show two identical SSID.

Regarding clients who are unable to connect to the nearest AP. Do you enable fast roaming? You could try manually lowering the wifi6 AP's transmission power so that devices farther distant from it do not connect to it. Alternatively, you might try adjusting the RSSI threshold so that clients that connect to the AP with a poor signal do not connect and instead connect to a better signal.

Regarding the issue of some mobile devices not connecting to EAP620 HD and EAP610, please try to disable PMF. If the client does not support the PMF function, the SSID for configuring PMF function cannot be associated with. 

How to configure PMF on Omada Controller

  @Alam0786 

As mentioned before, please try lowering the transmission power for wifi6 APs from high to medium or low, and set the RSSI threshold to around -60dbm.