Setting up mesh for dumb ap connection COVR X1862

I've got 4 COVR X1862 devices running with OpenWrt 23.05 and I'm a newbie to networking.
First device acts as router behind a TC4400-EU docsis modem with a dual stack connection from Vodafone. Second devide is a dumb AP connected via ethernet. This is running fine so far and I'm very glad to have come this far.
Now I need to set up the 3. + 4. AP as dumb AP aswell. The 2. AP only has a free ethernet port "internet" which can't be used for the next dumb AP I reckon so is the 802.11s mesh the only way to set up my remaining APs?

Is it possible to configure the mesh only through the interface? I've actually managed to get shell access but didn't come too far with the steps described in the wiki for "802.11s Based Wireless Mesh Networking".

Any help is very much appreciated :pray: