ok I managed to do it. Huge thank you to whoever you are. Just followed this:
A quick guide on how to put PTCL F670L fiber modem in bridge mode
blog.monib.xyz
View attachment 95762
Port binding I did to lan 1.
In my Asus router all I did was PPPoE and put the username and password. MTU was already 1492. No need to add vlan ID .
And this thread is appropriately named, same old BS indeed. The password they gave me for PPPoE was wrong. I tried ptcl which some suggested here and that worked.