After installation found no audio output from speakers, phone jack or through BT (BT mouse works well). Otherwise, as always beautiful Mate working well with one small glitch that network icon on the panel sometimes, after start, appears as two the same icons (one normal for panel size, another slightly larger). After restart of the computer the only one icon present. No effect on connection in any case.
Under Win 10 it has Realtek Audio Driver v.6.0.8988.1.
In Ubuntu-Mate 20.04 (also tried with 20.10) in sound preferences it show only one option "Smart Sound Audio Controller, 4 Outputs / 6 inputs, Play HiFi Quality Music".
Today, 2021-01-05, after OS software update I rechecked (with newer kernel) sound preferences dialog box again. No test sound from speakers again. However in input mode I noticed that Audio input bar was working, allowing level change. Honestly, do not recall to see it before. I am new to original Ubuntu-Mate, was using Robolinux-Mate before (still based on Ubuntu).
When I tried Flex with Mint and Manjaro there also was an additional option in Hardware dialog box: " Audio Adapter Unitek Y-247A with no audio out either.
Do not have audio from speaker, phone jack or through BT. When trying to connect to my trusted VTIN BH338A BT speaker in, during device setup I got message: "Device added successfully, but fail to connect".
Just want to add that 1:1 installation on Flex on external SSD came out with exactly the same results however booting it on 7 years old 15.6' HP Pavilion AMD A8 and 8 GB of RAM my Mate working just great (only had to deal with lower resolution and it is way slower boot time). Otherwise Audio works perfect, BT connects well and other than speed and only 2,4 GB WiFi no other problems found so far. Also it does not give any specific name for audio adapter.
Will be happy to provide any other info if someone can point me to specific ones. Sorry, I am not a computer expert. Done quite few installations on PC desktops and laptops of OS2/Windows and Linux OS in the last 25 years never had similar problems. But I like Ubuntu-MATE a lot, a specially how it runs nicely on my new Flex (other then problem above). It is blazing fast and stable (boots in about 9-16 sec, change Linux to Win 10 takes about the same time. So, I guess, probably someone will be able to figure out this issue in near future. On my part I like to help as much as I will be able to.
Thank you.