Using UniFi AP-AC Lite with MikroTik router on standalone mode

Hi, I am currently using 3 UniFi AP-AC Lite on standalone mode with a MikroTik router. I have a captive portal setup on the MikroTik but when a guest user connects to the free WiFi near a UniFi AP it doesn’t route them to the captive portal to put in information. Is there a way to make it so it does route it to the portal? They have the same SSID as the MikroTik and no password as its for a restaurant guest internet.

The MikroTik is connected to our main router that isn’t accessible by customers. I have made it so people connected to the free wifi are unable to view the main router.

Any help would be appreciated. Do i need a UniFi controller to be able to do this?

If you plug a laptop directly into the Mikrotik does the Mikrotik hotspot work? With a UniFi AP configured in standalone mode it should provide a transparent connection between WiFi and ethernet.

If you use a UniFi portal instead the controller has to be online all of the time, and you can only use UniFi APs as the portal redirection is handled by the AP.