I had this same problem after I installed Linux. I still wanted to turn my USB drive into a usable USB drive. I don’t remember everything I tried, but the following link is what finally worked for me:
https://www.pendrivelinux.com/restoring-your-usb-key-partition/
Hi @jof, today I found myself in the same situation, and got to a solution. If you used balenaEtcher, probably it will help you
To fix your broken usb, use this tool in windows to get it back. Windows 10 for some reason cannot format the usb, also not with the command options (diskpart).
Balena killed 2 of my usbs and i recovered it with this tool. Minitool partition wizzard free
More details: FIX - Etcher killed my USB - BalenaEtcher Fix - YouTube
It looks very interesting tool, but works in Windows only 
Sadly yes, thats how i recovered my usbs. I didnt try anything in linux yet.
I tried everything anything you can think of (including a command line in terminal) but gave up at the end. If someone comes up with a solution in Linux I'd love to hear!
In Linux, dd commands usually can save a USB stick that got Fried by Balena. It's been a while and I've not memorized them. But that may be a reasonable starting point.
I tried that also, but the USB seemed to be beyond repair.
Oh, well... Maybe that is why nothing worked. 
I found this Windows app was good for reducing size of C:\ and creating space on a Windows PC drive, before installing ZorinOS as dual-boot.