@stas.f 

Unfortunately like other router manufacturers TP-Link doesn't want to support OpenVPN with full support for VPN PROVIDERS.

The OpenVPN they have included is meant for business site-to-site not VPN Providers.

If you want full OpenVPN support for VPN Providers on a router (Like I have) you can get that with ASUS routers. (Or with third party firmware Like OpenWRT, DD-WRT, FreshTomato with specific router support). TP-Link makes great innovative hardware. Unfortunately they should invest more in their firmware support personnel and hire from overseas if necessary to get talent.

  @stas.f  For some time now it has been an 'Open Secret' that the Tl-ER7206 supports only OpenVPN as server, not client. You can at least partially configure it as client for OpenVPN, but it will not work. I have asked TP-Link about this NUMEROUS times - coming up on a year now - and the latest information I have on that from them was that it is slated to be fixed in a release some time this fall (a few months back I heard their dev team had it on their roadmap for the controller firmware revision 5.2 (which is now on 5.1.8). The last tme I complained to them about it I made it crystal clear that forcing people to use L2TP instead of OpenVPN for Client VPN connections severely limits the number of VPN providers the router owner can use as L2TP is old (and cracked by a variety of 9-eye governments) and supporting OpenVPN as client needed to be given a much higher priority in their development pipeline/schedule. This was about a month ago... They agreed. I was told today that it might not be in 5.2 but it would most definitely be this fall.... hope that helps. Sheesh... This is particularly painful for those of us who have bought into the Omada environment/controller paradigm.