Nokia C20 Plus

Nokia C20 Plus is an entry-level device released in June 2021.

Bootloader Unlock Theory
You may use the special fastboot binary compiled by Unisoc, which contains this command: fastboot flashing unlock_bootloader /path/to/unlock/key/file

Unisoc has a Linux binary available, in fact fastboot-android.exe contained in OST LA also has this command available.