I have a Hue V2 Hub, but I don’t use the App. So basically it is just an additional device, that I don’t really use.
Does it make sense to move to a dedicated Zigbee dongle like the Conbee II?
What are the pros and cons?
Can I still make Firmware updates or ist the App / Hub needed for that?
Can I setup new lamps without problems? I guess I have to remove the existing lamps from the App first and add it to Conbee II.
Doesn’t sound like you need the hub.
Zigbee2MQTT supports Hue firmware updates out of the box. ZHA didn’t, at least for my devices. ZHA does have some OTA firmware support, but is a more limited list than z2m.
Even with z2m, I don’t know if you can count on every possible update being available, as I think it is a community effort. That said, Hue is such a major player and the z2m so well established that I doubt any significant updates would be missed.
Well I am thinking about getting some aqara sensors, since they are a very good deal. In that case Zigbee is needed.
Is Zigbee2MQTT the best and most future proof way to integrate?
Z2M/Conbee works fine but do note that it cannot do firmware upgrades for a.o. the HUE devices. Now, I never (!) needed a firmware upgrade but just so that you know about the limitations
Pros and cons to both zigbee2mqtt and ZHA.
As the “native” zigbee integration ZHA is easier to get started with. Zigbee2Mqtt is more work to setup, but is easier to work with day to day due to what I consider wider and deeper device support.
Wider meaning it supports more devices, deeper meaning it will usually expose more attributes as HA entities.
Using the Hue motion sensor as an example, both z2m and ZHA will give you occupancy, illuminance and temperature entities, but only z2m exposes the sensitivity and timeout configuration options as entities. In fairness, the settings are accessible in ZHA if you look under the Manage Clusters dialog, but you have to know to look there, and then research or trial and error what values to use.
Similar differences in other devices. Beyond configuration entities, your much more likely to be parsing events and such in ZHA, where z2m will give a defined entity for the attribute you want.
Good point, I guess firmware updates are not really needed in the end. They are probably more for the communication to the hub.
I guess with this I should be able to install z2m:
https://www.zigbee2mqtt.io/guide/installation/05_python_virtual_environment.html#installing
What about the dongles, is the ConBee II USB Stick the way to go?
I could not tell for the others, I am happy with Conbee II even if it is 2.5x the cheap sonoff stick
Depends on what your setup is. I initially setup HA using hass.io.I just use the add-on for z2m. I’m usually a control freak and would setup separate VMs, containers, etc, but have been lazy with HA, and so far see no need to change.
I’d go with CC2652 based sticks, simply because the lineage was the originally supported z2m stick, and from what I can surmise what the developer @Koenkk uses.
I use the Sonoff Dongle Plus with @koenkk’s firmware. Originally a why-not-it’s-cheap-enough-to try option, it’s been 100% stable for me with great coverage and easy hands off firmware upgrades. Also has been much more reliable and trouble free than the Nortek HUSBZB1 stick I started with. If I ever change again, it will be to an ethernet connected option like tubezb, or maybe the existing stick hung off a Pi.
Yeah… I do like the ‘try’ part 
with THE caveat… when changing sticks one has to re-pair all and I had this situation already once when changing zigbee channel…not to be repeated too often. Still. I read lots of good stuff on the sonoff stick so nothing (!) against it
The Sonoff is not available, the ConBee II is.
So at the moment I would have to go with the ConBee anyway.
Just to be sure I don’t need a Hue hub anymore and I can easily add aqara sensors, right?
Actually I was able to back and restore from the Nortek to Sonoff without re-pairing. There are backup/restore procedures. At that point I was under ZHA. Not sure about zigbee2mqtt.
The migration from ZHA to zigbee2mqtt was done running them side by side for a while, so devices were all migrated and re-paired over time to zigbee2mqtt.
I still have ZHA installed and paired with a couple of devices just to give ZHA something to do. As previously mentioned, the Sonoff sticks are cheap enough, so why not keep the ZHA option available?
Any new devices I try under both, but so far they all end up in zigbee2mqtt.
There are other sticks based on the cc2652 family chipsets. Supported Adapters | Zigbee2MQTT
EDIT:
Want to make clear I don’t have ANY anti-conbee sentiment. I’ve never used it, so can’t speak to it. Conbee could be 100x better than the Sonoff for all I know. Just relaying my personal experience and thoughts.
Is there a need for a broker if I install like that?
https://www.zigbee2mqtt.io/guide/installation/05_python_virtual_environment.html#installing
I do have zwavejs2mqtt installed.
The “all add-on” version would be to install the MQTT broker add-on, the zigbee2mqtt add-on, and the MQTT integration.
If running zwave2mqtt, I assume you already have an MQTT broker installed then? And the MQTT integration?
The zigbee2mqtt add-on defaults a local broker, assuming your also using the MQTT broker add-on. If you’re already using another (non-add-on) MQTT broker, it should just be a matter of changing the url for mqtt in the zigbee2mqtt config file.
I have to admit, I disabled MQTT in zwave as I don’t need it. However, I don’t really understand the role of mqtt anyway. Especially as of why I need it with zigbee.
Also the zwavejs2mqtt is a mqtt gateway.
mqtt is a message broker which allows an open communcation between the zigbee device and a.o. HA…and similarly between zwave device and HA. You could go directly into HA with the zha interface as well but this is proprietary to HA…mqtt is ‘open’. In other words: zigbee2matt<>mqtt<>ha…can work in conjounction with zwave2mqtt<>mqtt<>ha.
Zwave doesn’t need the mqtt part. That’s why I disabled it. But I will look into that mosquito part.
you could use the zha intergation then, skip mqtt…it has less options wrt to devices but works OK so it seems (personally I have no experience). It would save another piece of software to maintain so if sufficient then why not 
That’s what I will do, thanks.
I’ve used both, started with ZHA because it was easiest to get running, but ultimately took the time to migrate everything to zigbee2mqtt.
IMO, the extra setup time for zigbee2mqtt is worth it. ZHA appears thinner and to have fewer moving parts (which I consider a pro), but I like living with z2m better. Others disagree, and I can see why, ultimately it is largely subjective with trade offs both ways.
Whichever you start with, I suggest trying both out before you get more than a handful of devices and automations.