I’m using HA for a year now. All my devices are DIY - ESPHome based . But now I don’t want to build devices anymore, especially when see lot of them to buy for cheap on AliExpress and need lot of them.
But, don’t know anything about Zigbee or Bluetooth devices and how to use them in the HA. So I need an advice what to buy and how to use it.
I have a three locations connected in local WiFi. Want to use new devices in all of them and control it from one HA server.
For start I need few switch like THIS which will control my HA switch entities. What will I need and on what I should look when buying?
Thanks for all and sorry for asking those noob questions 
For a start, don’t buy cheap on AliExpress.
Some of these devices work (generally the simpler ones), some sort of work, some work for a while and a few just don’t. The problem is that many manufacturers of low-cost devices don’t stick to the Zigbee specification and some generic products change without the model numbers changing.
Do your research. This may be a good starting point:
Although I think it’s maintained by users, so it’s hard to tell how up to date it is.
Good luck!
Ignore the fearmongering about Ali Express. Most of my dozens (note the plural) devices are from Ali Express and I have never had a DOA. I have had a couple of failures that were entirely my fault, except for one Z-Wave wall switch. From G.E.
Most of my devices are on WiFi, and a few Z-Wave switches. I only recently started adding Zigbee stuff. Other than the incredibly short range, I am impressed. So far. In Home Assistant I am using Zigbee2MQTT, with the MQTT part deselected. The short range of Zigbee is solved by having a lot of Zigbee router nodes areound the house. I added one of these in each room of the house and now there are no dead spots.
I am confused. Do you mean that you have three Home Assistant servers in different locations, like rental properties? If so, controlling all from one location is way beyond my pay scale.