Samsung devices previously displayed a condition “Prenormal” until Samsung Remote Monitoring had established that the phone was in normal use with a retail customer.
More modern devices do not reveal this. The install page https://doc.e.foundation/devices/gta4xl/install includes the note
Enable OEM unlock in the Developer options under device Settings.
It appears sometime that the OEM unlock option is missing from Development options, especially on new devices. Please connect your device to the wifi and check of system updates. After a reboot, the option should appear.
Have the device in “normal use” for 7 - 14 days with SIM card and Wi-Fi in operation.
These more modern devices seem to have increased security on the unlocking of the bootloader and don’t seem to respond to fixes, which worked in the past you already tried. Another consideration is that you are using the device in the region of the world where Samsung intended marketing. So an Asian intended market device might not ever release in USA for instance.