Losing 2nd GPS when compiling for EKF2

Hey there,
I’ve been working on getting the EKF2 running on a Kakutef7 board and had to remove quite a few of the modules and stuff from default.cmake to fit into flash.
Thing is, now that I have it up and running I can’t connect to my second GPS unit anymore.

I didn’t touch the serial configuration of that file so the only thing I could think of would be the issue with UART/ USART, is it possible that somehow changes between versions and I might have to connect it synchronous now or something?

When flashing a normal version (no EKF2) both GPS get recognized and used.
Also with the EKF version the GPS does get a fix as indicated per its LED, just not showing up in MAVLINK inspector.

So what would make the TELEM2 port not recognize a GPS unit? Any thoughts?

One more bit of info: with the “normal” firmware for this FC port selection in QGC shows only the actual available ports.
With my “EKF 2 version” it shows the whole entire line of standard px4 (like “cube payload”, wifi-radio, TELEM4, GPS1/2/3, etc.)

Thanks for reading and any advice will be very welcome. ,)