Dex does appear to be only for Samsung devices (Galaxy 8 and later releases I think).
They do have a wireless option if the monitor/computer/tv supports Miracast and you have a Galaxy Note 20 or newer
It’s really a full scale computer emulator (i.e., turn your mobile device into a computer). Seems like overkill if all you want to do is send texts and transfer files.
This recent summary article by the Android Authority does a pretty good job of explaining how it works.