Ubuntu – Windows 10 update ruined by Windows/Ubuntu dual boot

I had a Ubuntu/Windows 7 dual boot set up on my laptop. An updater tried to install Windows 10 in the middle of the night and now when I start the laptop, I get the grub rescue prompt. I tried this solution but ls into any partition gives me unknown filesystem.

I installed the boot-repair utility with a Live USB and ran a "Recommended Repair", which after a few minutes reported it had ran successfully but the grub prompt was there waiting for me when I restarted the laptop. Incidentally, most of the advanced options are grayed out. Here's the boot info summary.

I then tried to repair/restore using the Live USB assuming sda1 to be the Linux partition but chroot gave me failed to run command ‘/bin/bash’: No such file or directory. Taking a closer look at the boot into summary, the boot sector type is listed as Windows 8/2012…

I'm losing hope that I'll be able to recover any of my data :/ Any advice would be greatly appreciated!

EDIT: Thanks to oldfred, I can access both Ubuntu and Windows 10 from the grub menu at boot. In order to restore Windows 10, I booted from an Ubuntu Live USB and ran:

sudo apt-get install syslinux
sudo dd if=/usr/lib/syslinux/mbr.bin of=/dev/sda

Windows didn't register my Ubuntu ext4 within an extended partition with the swap space. This was resolved, again from the Live USB, with parted:

sudo parted /dev/sda unit s print
sudo parted
(parted) unit s
(parted) rescue

Input start & end and see if it finds partition. If a new partition is discovered, install boot-repair and run "Recommended Fix" to reinstall grub. Check out the solution comments for more details!