The DLink DWA-X1850 - AX1800 Wi-Fi 6 USB 3.0 Adapter uses a Realtek chipset according to DLink.
I hope Mediatek or Atheros or Intel makes one 
I think Realtek drivers suck.
Has anyone heard about any good wifi6 USB devices?
I built my own router out of a raspberry pi4 and better wifi is good.
There have never been half-decent 802.11ac USB wireless cards on the market, chances for that to change with 802.11ax are slim to none.
// edit 2022-03: to build for newer kernel versions, use the fork from lwfinger instead:
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I acquired this device recently (was released only a couple weeks ago), and it's running perfectly on Linux, however currently with the Realtek proprietary driver.
The only other USB ax device currently on the market is the ASUS USB-AX56, which uses the same RTL8832AU chipset, which is the 2-strem variant of RTL8852AU.
A driver was pushed on github recently, I forked it to add the DWA-X1850 USB VID/PID:
Basically, just checkout this repo, make and sudo make install.
USB modeswitch is achieved by ejecting the USB Mass Storage device.
The Linux Wireless Driver for RTL8852 will be called rtw89 and is supposed to be included for Kernel 5.16:
https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next.git/commit/?id=e3ec7017f6a20d12ddd9fe23d345ebb7b8c104dd
However, it seems currently only PCIe is supported, but I guess USB devices can easily be added later.
Is it a new driver?
I remember hearing in the past that realtek usb drivers were not good enough quality to be included in the kernel.
Maybe the one on github is better.
That is very unlikely to happen.
The one on github is from Realtek, i.e. the one that is offered to device manufacturers.
The rtw89 driver in the next-branch of Linux Wireless was also co-authored by Realtek, but it is structured more "correctly" to be included in the kernel.
I guess the difference between PCIe and USB versions is greater than just affecting the transport protocol for device commands then. Maybe supporting USB devices on Linux is still considered to be vendor's duty.
I think the main motivation for rtw89 is that certain Lenovo devices come with this chipset, and ThinkPads have always been the iconic hacker's laptop... 
Realtek wireless is devided into two semi-separate business entities, reasil (the USB side) has been ignoring mainline development for the last 1.5 decades, the PCIe division however is more involved. I haven't seen any indications of this changing, so I wouldn't expect any assistance from reasil.
Does the driver support creating 5GHz APs?
I will buy a DLink DWA-X1850 it has an in-kernel driver.
Are there any wifi6 PCIe cards available with Realtek chips?
All I saw when I bought one was Intel AX20x chipsets.
Thanks, I was not aware of that.
It seems we have to stick with the Realtek proprietary kernel driver for a while then 
hostapd looks good so far, I can connect to the DWA-X1850 with my QCA AC1200 card on 5GHz:
$ sudo /usr/sbin/hostapd /etc/hostapd/hostapd.conf
Configuration file: /etc/hostapd/hostapd.conf
Using interface wlx0c0e766c080f with hwaddr 0c:0e:76:6c:08:0f and ssid "dlinktest"
wlx0c0e766c080f: interface state UNINITIALIZED->ENABLED
wlx0c0e766c080f: AP-ENABLED
wlx0c0e766c080f: STA 9c:b6:d0:0e:9d:7d IEEE 802.11: associated
wlx0c0e766c080f: AP-STA-CONNECTED 9c:b6:d0:0e:9d:7d
wlx0c0e766c080f: STA 9c:b6:d0:0e:9d:7d RADIUS: starting accounting session 6BCB853C6D64D470
wlx0c0e766c080f: STA 9c:b6:d0:0e:9d:7d WPA: pairwise key handshake completed (RSN)
But I could only test 5GHz in ac mode, I guess my hostapd version is too old... 
Line 3: unknown configuration item 'ieee80211ax'
wikidevi lists a few PCI VEN/DEV ids here, but they seem to be mostly OEM cards built into laptops:
Guess it will take a little while for retail cards to hit the market.
By the way, it seems someone made a fork of rtw89 for USB devices here:
https://github.com/neojou/rtw89-usb
Maybe I can find some time to test this over the weekend.
It seems we have to stick with the Realtek proprietary kernel driver for a while then
Is it available in an openwrt package?
I want to use it as an AP on a Raspberry Pi4.
Non x86 platforms have more chances of driver bugs. 
This seems promising.
How is the Realtek version of rtw89 different than neojou's rtw89-usb?
Both support the DWA-X1850 which is usb.
Both have source available on github.
If any of them would ever be available as an openwrt package, then rtw89, but only after it made it into the the kernel... and openwrt switches to 5.16 (or whatever version it will be in), and finally someone creates a package for that driver. Currently, this does not contain USB, the rtw89-usb is just a fork by someone.
The Realtek proprietary driver is offered to OEMs to support their devices on Linux, but it will most probably not meet the quality / code structure expectations of kernel maintainers (so you cannot blame it on Linux folks when that driver crashes your kernel).
But again, for my personal needs it works well enough at the moment.
If you read through pdfs in the documentation folder, there's a lot to learn about how to customize it etc., it is configured to build on x64 by default, but ARM and MIPS are claimed to be supported as well (there are Makefiles for several common SoC families in the platform folder)
Currently, this does not contain USB, the rtw89-usb is just a fork by someone.
Didn't you show the rtw89 driver running an AP on the DWA-X1850 (a USB device).
No, that was the Realtek one. I may find some time to test the other one over the weekend, but for the moment there seems to be no need for that, also I couldn't yet find the spot where to add USB vendor / product ID...
I'm confused, isn't rtw89 the Realtek one and didn't they put it on github?
You forked it to add the DWA-X1850 USB ID?
Realtek did not put anything on github, someone leaked their driver (RTL8852AU_WiFi_linux), I added the USB VID and PID for D-Link and tested hostapd.
rtw89 is an open source driver developed by Linux people, with some help of Realtek employees, which currently only supports PCIe card, e.g. as those found in newer Lenovo ThinkPad models. This driver is currently in the next branch of Linux Wireless, and is expected to be included with kernel 5.16.
Someone forked this to add USB support, but I just found that on github an hour ago, have not tested this, i.e. not even figured out how to add USB VID/PID (maybe just needs a udev rule).
rtw89 is an open source driver developed by Linux people, with some help of Realtek employees
Do you have any idea how it performs against the proprietary one?
I hope linux-wireless uses this one but I won't get my hopes up.
It seems it is still a ways off for having open source support.
I hope someone will develop a mediatek wifi6 USB device.
They seem to be the only company left that has good open source support for recent chipsets.
I joined the linux-wireless mailing list and did a search of the archives to rtw89 and found this:
works flawlessly with an USB wifi stick
This the first Realtek driver that seems promising.