I can't get my thumby's to connect to the web editor on Linux (Debian 11 and Fedora 36) the same thumby, cable and PC work in windows.
lsusb shows a MicroPython device in it and it also works in BOOTSEL (holding the down button while turning it on)
listing /dev/tty* doesn't show a ttyUSB device
Try adding your user to the dialout group: sudo adduser $USER dialout
You may need to log out and back in or reboot afterwards