Can I safely restore Windows while keeping my Linux partition?

Solution 1:

Restoring Windows will almost definitely break grub, and likely overwrite your linux partitions. You need to backup everything before the restoration, as you'll most likely be reinstalling Ubuntu after it's finished.

Solution 2:

• There should be no problems on default Windows 10 installations (UEFI).

  I just had to reset one of my Windows 10 installations due to a Windows update error (which I could fix this way) and none of the Grub installations (one SSD with Ubuntu; one HDD with Windows 10, Ubuntu and Fedora) were touched.

• Method used: Settings → Recovery → Reset this PC → Keep my files