Hi Martin,
Experiencing exactly the same issue as you (have opened a discussion on Reddit, here).  The only solution I've been able to think of is getting pigtail adapters from eg: Amazon (I believe these would work) and running them through the bulkhead holes in the back of the case.  I haven't been able to find any official Dell cables that would do the job.

Hope that helps,
Matt

Hi Martin,

I posted before I found your thread, my final tag of Intel AC 9260 highlighted your post. Did you get a resolution, as I am in the same boat?

https://www.dell.com/community/Optiplex-Desktops/Optiplex-3070-MT-PCIe-WLAN-NIC-Intel-Issues/m-p/7468836#M38753

the typical PC is a great faraday shield.  so it needs and external antenna to make any radio device work best.

moving the mini card off the main PCI-card, gets you no antenna.

no OS stated at all,  w10 64bit,  v1909, is it.

the drivers are not at DELL they are at ASUS.com

and must match your OS or will not work.

the chicken and the egg is the reason, this fails 9 out of 10 times, after all a tech, connects ethernet first

then and only then can the PnP work  see that DM icon there, called unknown. click that and update it.

or force the driver by hand from ASUS to USB stick and then run  that driver from there, installed.

one can put any PCI-express card (short) in SFF X1 slot vast cards works, using a real driver.

why not load that first. then add the card second as the maker told you on their support page.

load this FIRST< run the driver. installer

then plug in the card, no AC LINE CORD !  do not hot swap cards ever.

this is all basic stuff here, from 1995 to now. Pnp plug and play only works if Ethernet cable connected

Ethernet connects in like 10 seconds. why not do that first, see if the MS PnP drivers load. from MS servers same.

if not, ASUS.com  is it.