I did some more experiments.
I exchanged the firmware blobs for the MT7925 with the most recent one on: linux-firmware
This is not ideal, as it keeps the linux diver (part of the kernel) unchanged but changes the mediathek provided firmware blob used by the kernel. (On Bazzite this can be done with OverlayFS.)
I didn’t do poper testing with the original and then changed firmware blob, but I compared it to another laptop with an old Intel 8265 / 8275 I have. Both latops are the identical framework laptop only the network card is different and the performance difference is significat:
Mediathek: 20-26 MBits/s (Exchanged Firmware, 5GHz)
Intel: 184-192 MBits/s (5GHz)
Mediathek: 43-58 MBits/s (Original Firmware on Bazzite, 2,4 GHz)
Mediathek: 18-25 MBits/s (Original Firmware on Bazzite, 5GHz)
The laptops are placed back to back and use the same desk and use the same wifi connection. In theory Meidathek should be a lot faster as it can use MIMO and Intel can not, but as we can see, that doesn’t really matter if you driver/firmware is broken.
In a nut shell, I don’t expect any significant improvement of the Mediathek with kernel 6.19 and thus I will try to give back the Mediathek chip and request another chip.