ITead (of Sonoff fame) has announced that will soon sell an inexpensive Zigbee 3.0 USB dongle based on Silicon Labs EFR32MG21 which is a very powerful MCU with an integrated +20 dBm radio amplifier.
Update 2021-40-16: Firmware released with it has a bug so it requires a firmware upgrade before use.
Update 2021-03-16: ITead have manufactured a limited production run and now sell it for $$6.99 (US):
ITead Zigbee 3.0 USB Dongle Model: 9888010100045
They have posted a video on ITead’s Facebook group for Sonoff showing this new dongle working out-of-the-box with the ZHA integration for Home Assistant (via the bellows radio library for its zigpy dependecy), however since it will come with the standard Silabs EmberZNet (a.k.a. “Ember”) Zigbee NCP coordinator firmware with its default EZSP serial protocol interface enabled so I believe that it should also work out-of-the-box with OpenHAB Zigbee Bindings too if it now supports EZSP v8?
In that video, they mention that they are targeting DIY home automation users and testing Silabs EmberZNet 18.104.22.168 firmware on it to ship it pre-slashed for compatibility with ZHA for Home Assistant. EmberZNet 6.7 introduced EZSP v8 which uses a new framing format and expanded command id field from 8 bits to 16 bits. They also mention in the video at this EFR32 Mighty Gecko Series 2 dongle will ship with firmware config for 115200 bit rate speed by default so might have to change flow control configuration in OpenHAB Zigbee Bindings?
I have asked ITead via e-mail and been told that their design phase is completed and got the information ITead will initially only sell this Zigbee 3.0 Dongle without an external antenna (no SMA-connector or IPEX connector, so a built-in circuit board antenna only) and without a plastic-case as an enclosure (same as how they sell their CC2531 dongle today). I was also told that this new dongle will use the exact same Silabs SKU for the EFR32MG21 chip that is used on the board inside their Sonoff ZBBridge Zigbee Bridge (which can use as an alternative Zigbee to WiFi bridge if flashed with Tasmota and other Zigbee coordinator firmware).
I have no idea if they started production run or when it will available for purchase, however, my guess is that it will be sold at a relatively low price from their China store considering that their existing Zigbee Home Automation 1.2 dongle cost $3.99 and their Sonoff ZBBridge cost $16.90 in their China store.
Updated thread with price + links and some new information from ITead after the product was released.
Older and newer firmware as linked to by ITead:
Elelabs EZSP Firmware Upgrade Utility can be used to flash the firmware to a newer or older version: