Need help: cannot jailbreak unactivated & activation-locked iPad Air 1

[yokoiwa]

machine info

iPad Air 1 (Cellular) (iOS 12.5.5)

• Activation-locked : I lost iCloud account
• Unactivated : shows Welcome screen

software

checkra1n (v0.12.4 beta)

details

GUI mode

1. connected iPad to Macbook
2. launched checkra1n
3. checkra1n turned iPad into Recovery mode
4. followed instruction to turn iPad into DFU mode
5. but iPad was rebooted in Recovery mode again

CLI mode

1. launched checkra1n in CLI mode
2. turned iPad from normal mode into DFU mode manually
3. connected iPad to Macbook
4. checkra1n started manipulations
5. iPad was rebooted in normal mode (seems nothing changed) and checkra1n shows "Unknown error (error code: -20)"
6. Even when I tried -s option, the details were same

Anyone has some idea? Thanks in advance.

[cinderblocks]

Experiencing the same on iPad Mini 2 unactivated