Google announced the end of support for early Nest Thermostats in a support document earlier this year that largely flew under the radar. As of October 25, first and second generation units released in 2011 and 2012, respectively, will be unpaired and removed from the Google Nest or Google Home app.
Users will no longer be able to control their thermostats remotely via their smartphone, receive notifications, or change settings from a mobile device. End-of-support also disables third-party assistants and other cloud-based features including multi-device Eco mode and Nest Protect connectivity.
Matter is more of a higher level IoT coordination protocol.
Zigbee and Zwave are radio protocols (relatively long range, low energy).
The neat thing here is you can bridge a lot of shit into Matter, and then use almost anything you want to control all the different devices. Everything becomes visible in the same control panel regardless of connection type and manufacturer. Everything becomes available for automation tools too!
If you run the software Home Assistant on a computer at home then it can act as your IoT control server, and giving it radio antennas for Zwave and Zigbee will let it act as a bridge to relay commands to devices that use those protocols (like a ton of small lights and sensors and more).