Does anyone know how to extract files from a win 10 hard drive? My neighbor's laptop blew the mobo and she needs some files from her old drive. I'm attempting this with Ubuntu 16.04 x64.

Welcome to LinuxQuestions.

I don't remember if ntfs-3g and fuse was automatically installed in 16 but since it went EOL in 2021 its main repositories are no longer active but you might be able to switch to the archive repositories by changing the /etc/apt/sources.list to:

http://old-releases.ubuntu.com/ubuntu xenial...

Otherwise if able download a newer live version and run it from USB. Hopefully the filesystem is not corrupted since by default W10 hibernates. Anything still open or in the journal might be lost. You might need to use the -f option to force mounting the filesystem.

Should mount automatically, even with that. Try mounting it and check the messages. With the disk connected, show us this (might need sudo).

Or you could make a bootable USB from Ubuntu or dedicated recovery distro and boot your system from that.

I'd either use a 'live' distro, or remove her drive, & connect it to another computer with a USB to SATA cable, mount it, & copy all the files off it.

Thanks for the info, folks. I did a forced mount with the drive on a usb dock and got her pics and docs to a flash drive.

Pics and docs?

Suggest her to make some backups...