The 9020 Micro does not have an M2 WIFI slot.

7260 WIFI

Actually you are both correct. There were 2 different 9020 Micro systems available. If ordered with WIFI then it came with the 7260 card. But if ordered without WIFI then there is not a capability for an M.2 card. the Dell Tech support page below offers a little more information.

https://www.dell.com/support/article/ca/en/cadhs1/sln300826/optiplex-3020-9020-micro-systems-manufactured-without-an-internal-wireless-network-adapter-cannot-have-internal-wireless-installed-after-purchase?lang=en

Actually, it does. The Intel 7260NGW is what in there now, and it goes in the slot labeled SLOT 1_M.2

It looks like this.

Still looking for possible replacements other than the same model card. 

Again, research seems to show this card has a lot of known issues.

I'd like to replace it with another younger model Intel card.

Any help would be appreciated. TIA

I have one with WIFI and its exactly the same as the posted picture and its NOT in the M2 slot.

7260 WIFI

I stand corrected but a bit confused. According to the Intel product brief the connection is M.2 so the question becomes, was there more than one form factor available? And speedstep I yield to your knowledge of the system as you have far more experience on that model than I.

From the specs..

Feature Specification

I do not think that DELL KTTYN fits into a 9020 micro.

The 9020 Micro is the EXACT model that I own.

The Dell internal SPMD (spare parts master database) does not help with the confusion. When I look up Optiplex 9020M, it list these =

GPFNK Intel Wireless 7260AC M.2, Wifi (802.11 ac/a/b/g/n)/Bluetooth 4.0
KTTYN Intel Wireless 7260AC M.2, Wifi (802.11 ac/a/b/g/n)/Bluetooth 4.0
5K9GJ Intel Wireless 6235, Wifi (802.11 a/g/n)/Bluetooth, MiniCard
9VVTM Intel Wireless-N 7260AGN, WiFi (802.11agn 2x2)/Bluetooth 4.0, Half Minicard

9VVTM is what mine has.

The 9020M, Micro, regardless of it being purchased with or without WIFI has 2 M.2 slots and the 9020 USFF has one Mini PCIe slot.