Could you please point out to specific adapters you used?
I have a couple of XTRX cards, having issues with initialization on x86 running Linux,
PCIe x1 → mPCIe adapters listed XTRX in only 1 out of 3 motherboards, and only in x1 slots (not X16). The XTRX is rapidly flashing both LEDs in all boards.
M.2 → mPCIe adapters did not work at all (XTRX is flashing one LED slowly),
Could anybody suggest where to start looking regarding PCIe devices initialization (BIOS settings were not helpful)
There’ve been some boards without some crucial component fitted on the board: XTRX not found - #12 by ricardas
I had that one missing, and the XTRX had real struggle being detected on some configurations. So make sure it is fitted for you. If not, you can just put a solder bridge (that’s what I did).