It's is M.2, but not the M/B+M key most M2 SSDs use but rather a A+E meant for WIFI/Bluetooth. According to this video it's essentially 2 PCI Express x1 lanes and USB 2.0. The video goes on to explain some possible alternative uses:
A gigabit ethernet adapter
2x SATA ports for a standard SATA drive
Coral tensor processor
SD card reader
2x USB A-type ports
Some type of SIM card adapter (video wasn't quite sure on it either)
A PCI Express x16 slot that only functionally works as a x1
So while does this slot has it's uses, it's not meant to be used for M.2 drives but rather WIFI.
it's essentially 2 PCI Express x1 lanes and USB 2.0
Sometimes there's only a single PCIe lane though. And as you say, that's not a x2 but explicitly two x1s.
No WiFi card needs the bandwidth (yet), at PCIe 3 speeds you've got around 7.8Gbps for a x1, and PCIe 4 double that.
The Coral comes in a "dual" version for exactly this reason (https://coral.ai/products/m2-accelerator-dual-edgetpu/) you just have to be very sure the slot you're putting it in is actually delivering two PCIe connections.
Also for bonus fun, most WiFi/BT cards use the PCIe interface for the WiFi and USB for the Bluetooth.
Sure, but there are several and op didn't specify what they wanted to do with it, typically if someone uses the m2.22xx naming they expect to put storage in it, which would not work here. So I was just trying to make that especially clear.
They should work on most computers, but some machines have a whitelist of supported WiFi cards and ignore anything else you plug into the slot for the WiFi module.
It looks like it is one, but dmidecode doesn't show it.
# sudo dmidecode --type slot
# dmidecode 3.4
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.
Handle 0x001C, DMI type 9, 17 bytes
System Slot Information
Designation: J6B2
Type: x16 PCI Express
Current Usage: Available
Length: Long
ID: 1
Characteristics:
3.3 V is provided
Opening is shared
PME signal is supported
Bus Address: 0000:ff:10.0
Handle 0x001D, DMI type 9, 17 bytes
System Slot Information
Designation: J6B1
Type: x1 PCI Express
Current Usage: Available
Length: Short
ID: 2
Characteristics:
3.3 V is provided
Opening is shared
PME signal is supported
Bus Address: 0000:ff:1c.4
Handle 0x001E, DMI type 9, 17 bytes
System Slot Information
Designation: J6D1
Type: x4 PCI Express
Current Usage: Available
Length: Long
ID: 3
Characteristics:
3.3 V is provided
Opening is shared
PME signal is supported
Bus Address: 0000:ff:1d.0
Handle 0x001F, DMI type 9, 17 bytes
System Slot Information
Designation: J7B1
Type: x1 PCI Express
Current Usage: Available
Length: Short
ID: 4
Characteristics:
3.3 V is provided
Opening is shared
PME signal is supported
Bus Address: 0000:ff:1c.5
Wrong DMI structures length: 3135 bytes announced, structures occupy 3136 bytes.