Galaxy s8,s9 will not connect via USB to Zorin OS 15.3
I need to connect my phone, S8, to my desktop via USB. My S6 had no problems, but neither the S8 nor the wife’s S9 will mount. I have Zorin Connect running on both devices, and I had them paired over the network, but I need the S8 to be mounted via USB. I am live testing Kodular/Thunkable apps. Any pointers are greatly appreciated.
-Kevin
Some suggestions here that you can try: https://community.sprint.com/t5/Samsung/Cant-find-USB-setting-on-Galaxy-s8/td-p/1041213
The “Solution” did not work for the poster of that thread.
I have already turned on the USB debugging.
Thanks for the pointer though. 
My Galaxy S7 never had any trouble tethering. I know that this will sound goofy… But I would suggest testing this with both phones against several USB cables. USB cables are often made differently and… some are made with cut corners, too. No matter how much a manufacturer claims them to be bonafide.
Sadly, these days, the odds of running into two such cables are higher than they should be. This really should be the starting point, with hats removed and head respectfully tilted in acknowledgement of how sad it is that it should be.
That aside…
This thread has multiple suggestions- including the debugging option which you can ignore. As you read through- you can place your bets on how many were accidentally and unknowingly resolved by the poster switching cables without thought. One poster even mentions that the solution seems no longer needed and knows not why.
Some suggest changing the Mac Address. Some suggest disabling the modemmanager.
I too, do not understand why changing the MAC address would help. If I could connect to do that, I wouldn’t need to.
I’ve got the same problem with my S9 as my S8. They use different cables. My S6 had no problem.
Samsung obviously sucks for fiddling with the USB connect in order to “protect us” from ourselves.
I was hoping Zorin connect could “connect” via USB, but I’m not seeing any solutions.
In a search while scanning down the results, I saw this line:
The problem was in Samsung Firmware after update to G960FOXM9ETF2 it fixes the problem.
Zorin connect is for use wirelessly whereby your mobile device is connected to the same wifi network as your PC. Since I have changed ISP to one that has a Static IP, I get reconnects with KDE connect (Same as Zorin connect - not tried Zorin connect yet - having some IP issues between this machine and router (but not on FerenOS - weird!)
Samsung S8 is up to date. According to Samsung, they removed the ability to connect via USB unless you are using Windows or Mac. Everyone who is having this issue should contact Samsung and complain…long and loudly.