Attach the EXT4 drive to a working Windows computer as a secondary drive.
This is a technical report regarding the recovery of file systems using the software GetDataBack Simple (often searched for as "GetDataBack EXT4" or "GetDataBack for Linux File Systems"). getdataback ext4
If multiple "candidate" file systems are found, select the one that matches the original size and location of your EXT4 partition. Attach the EXT4 drive to a working Windows