I'm on ubuntu 22.04 and I can connect over adb to my Samsung Galaxy A50, and do
adb reboot bootloader
it reboots to bootloader mode, but I can't use
fastboot devices, it returns empty.
Other phones work in this computer.
Bus 001 Device 015: ID 04e8:685d Samsung Electronics Co., Ltd GT-I9100 Phone [Galaxy S II] (Download mode)
All tutorials talk about a Windows driver, but what do I do for ubuntu?