Post#2 - (Not so Final) Final update : Alright, so never say never again. While I haven't changed my opinion about a ConBee 2 versus this Gateway, there's an advantage for just getting Xiaomi devices into Hubitat if you're using Home Assistant Device Bridge with the Mijia Multimode Gateway.
This new HA integration is only available if you have the Home Assistant Community Store installed, which is really easy to do. Once installed, there's a Xiaomi Gateway 3 integration that will allow you to obtain a token from the device and connect it directly to HA, without the limitations of HomeKit (e.g. You can use the Aqara Temp/Humidity sensors and it will include the Barometric pressure readings too). You'll be able to see everything supported by Home Assistant Device Bridge in Hubitat! 
However, this does limit you to Xiaomi supported devices and it's not fast. There's a noticable delay when a contact sensor triggers. It's not huge, but you can see the same delay if you connect the Gateway via HomeKit Controller. This might be due to the WiFi, or it may just be a limitation of the Gateway itself. In any case it's possible to get all the parameters from Xiaomi devices using the method, but it doesn't have the same lightning fast reaction time I experience with the ConBee 2 and the Zigbee ZHA integration in HA. Maybe if you install an Ethernet port in the Gateway (yes, it looks like that's an easy hardware hack you can do), but I'm not going to try that myself (at least I have no plan to do that at this moment). Would be interested to hear if anyone else tries it though and can confirm if the response is any faster over ethernet.
Here are some links to get you started if you want to try this out. There is one particular thing that you need to do, and it took me a while to notice this requirement. You need to open telnet on the Mijia Gateway. If you don't do this you wont be able to see paired devices and you won't be able to downgrade the device firmware if you want.
One thing that is especially nice about this integration is that you can disable firmware updates so they cannot happen automatically (currently Xiaomi doesn't do this) and you can prevent yourself or someone else with access to the Mijia Home app from accidentally or intentionally updating the firmware if that's not what you want.
Replace what is on the open telnet command line by pasting this command with no changes
`{"method":"set_ip_info","params":{"ssid":"\"\"","pswd":"123123 ; passwd -d admin ; echo enable > /sys/class/tty/tty/enable; telnetd"}}`
How to setup the integration
The video (in Russian) of how to do it
Here's how to open the case
You can install external antennas
You can install an Ethernet port
A page with flashing methods (can be done easily with Telnet) and several VERY hacky examples of adding an ethernet port at the bottom of the page. Page is in Russian, so use Google Translate if you don't speak the language.
One final note. You can apparently set the gateway with this integration to use the Zigbee ZHA to join devices (limited to the supported third-party devices shown in the Mijia app), and that doesn't disrupt you from still using Bluetooth devices with it. However, I couldn't get the socket to open on my virtual HA install, and I don't want to go through the hassle of removing ZHA on my primary HA install to test. But, even though the author demonstrates some additional abilities from downgrading the gateway firmware, they don't seem that compelling to me. You decide. One thing that was said to not be possible with the latest firmware was the ability disable the beeper. But in fact this does work. I did find that you sometimes cannot get options like "lock firmware upgrade" or "device paring" to turn on or turn off unless you reload the Xaiomi Gateway 3 integration. Not that big of a deal in my opinion, but something to keep in mind.
So for just $43 USD ($54 CAD) you can 
