Oh no - does this mean that I would not be able to use even a management vlan for the remote EAP215 and any omada devices beyond the remote EAP215? This would be very important to clarify...

  @ColleLupi 

Your problem with the management VLan can be set via Omada under Devices. However, this does not solve our problem. 
With several locations spread over an area of approx. 5km, the directional antennas must have Vlan passthrough. As the individual WLAN networks must be separated.
The EAP 215 Bridge cannot be used in this way. We have made a few speed and distance measurements. The performance of the bridge stops after just under 500 metres. 100m 160 down/20 UP, 500m 60 down/ 12 UP.
The old devices such as CPE 710 still have a performance of 140/20 after 3km. 
Unfortunately, we have already thrown away the required original packaging for a return. We have never returned a device out of over 100 Tp-Link devices. Times are changing.
 

  @ColleLupi 

Hi

Sorry, I was wrong. If the VLAN configuration is correct, the VLAN SSIDs should also work on the client side. To locate the reason, we create a support ticket to collect more information. Please search TKID240957552 from your email inbox. Thanks.