Xiaomi sensors - gateway problems / deconz/zigbee2mqtt

Hi everyone,

I got a bunch of Xiaomi stuff I would like to implement in the house. Temperature sensors l, door sensors, vibration sensors etc.

I first thought I would go for Zigbee2MQTT, but after waiting months without getting my items for it, I bought a Mijia gateway(v3 upgrade version). I decided to set it up on a VLAN, isolated from the rest of my network, but I have not had much success setting it up.
What is the current status of this? I see a ton of people have had issues with this, and just using the gateway in general with hass.

If I block everything and open port 9898, have igmp snooping and MDNS on in my UniFi, I cannot add the gateway to hass. It does discover it, kind of, but then I get a message that it cannot discover it. If I remove the block so the VLANs can talk together, and still keep the gateway off the internet, I had luck discovering it in hass a few times. However it does not seem like it is working properly, and I keep getting invalid key in log. I even went and reset the gateway and obtained a new key from an android tablet, but still, same.

Now I really just want something that works and is easy and reliable. My zigbee2mqtt parts just arrived, but I am not sure if I should go with that for what I am looking for? I hear the range is horrible. I am prepared to spend money on a stick for deconz if that works great? Or is it possible to get to a good place with the gateway?