Just confirming that rizvanrp's custom router with Unifi router as VLAN bridge guide (https://rizvanrp.com/pub/unifi_athena_my/custom_routers.php.html), works with the L7-N-R2000 router provided by TM.

Using Method 2, at Step 6, you will realise that the "My Internet Connection is" dropdown is disabled. To bypass this, use Google Chrome to do the setting, press F12 to open developer tools, click on the magnifying glass and then click on the disabled dropdown. Press F2, and erase the word "disabled". I couldn't save the settings with a blank MAC address, but leaving the existing one there was fine.

At Step 11, I had to choose "Bridge" for "My Internet Connection Is", instead of the Static IP option.

Lastly remember to call Unifi centre and ask for your Unifi PPPoE password, because if you copy the password from the source code it doesn't work (encrypted).