Found in https://www.reddit.com/r/linux/comments/11pkgjv/how_to_use_ext4_filesystems_in_windows/
Worked for me using an ext4 formatted USB HDD with Win11 and wsl2 on PowerShell(Admin):
Access Linux filesystems in Windows and WSL 2
If not installed, install wsl2 with PowerShell:
wsl --install -d Ubuntu
Restart Wn11 and find your harddrive id with PowerShell:
wmic diskdrive list brief
Mount the harddrive with wsl2 in PowerShell, in my case e.g.:
wsl --mount \\.\PHYSICALDRIVE1 --partition 1
Open Windows File Explorer, navigate to the mountet partition to access the files:
Linux\Ubuntu\mnt\wsl\PHYSICALDRIVE1p1\
On mine it ended up: \\wsl.localhost\Ubuntu\mnt\wsl\PHYSICALDRIVE1p2
Also: https://superuser.com/questions/37512/how-to-read-ext4-partitions-on-windows