dongle is the word I was looking for.
I am new here.
I have rewritten my three posts to make only one. post.
I came here to learn a solution about a driver problem with the
Ralink Rt3090 Half Mini Height Wireless N Card 802.11.
It seems that all Linux Mint version hate this card.
I have tried Linux Mint 20.1 “Ulyssa” MATE and
I had tried Linux Mint 19.3 “Tricia” MATE and both lost the WIFI connection.
I think that for some reason the driver rt3090PCIe is replaced with a generic rt2800pci in all Linix MInt ISO.
I looked all over the net and the only drivers I found are for Windows
[https://www.catalog.update.microsoft.com/Search.aspx?q=Ralink%20RT3090%20802.11n%20WiFi%20Adapter]
I bought a TL-WN725N at Dell.ca.
It is supposed to be compatible according to
Best USB WiFi Adapters for Linux (Review) in 2021
I received the TL-WN725N ordered from Dell.ca .
I put it in the first the USB port I saw.
I started the computer.
I got networks. 
Now I think I’ll get a driver because the speed is tooo slow.
In the TL-WN725N box, there is a cd rom.
The following is the only note I found on that CD :
For Linux users, please visit the TP-Link support website, find and download the compatible version of driver for your network adapter at www.tp-link.com.
And, of course, on the TP-LINK website I find
Operating System: Linux (kernel 2.6.18 ~ 4.4.3) beta version
Operating System: Linux (kernel 2.6.18 ~ 3.19.3)
when mine is
Linux version 5.4.0-62-generic
I think I may go back to Windows 7 but before I will update the MX-19 ( patito feo ) this must be greek, right ?