@Hank21 I reconnected AP, forgot it And readopted. Now I am waiting if problem persists.

Disconnecting after update to newest firmware 5.1.6 EU. I have no problems before update. It is under linux controller 5.14.0.11.

@Tedd404 I think that OpenVPN solution is discussed here https://community.tp-link.com/en/business/forum/topic/653224

@Clive_A I am using PPPoE VDSL connection. IT IS not possible to switch to different WAN connection type. I am using DSL modem which I cannot put in different mode (other than bridge mode).

I am using ER605 v1 which is better, but this gateway lacks power for max speed of my internet connection for VPN.

Not yet, I am using PPPoE (VDSL).