dual boot( win10 lubuntu 16) convert mbr to gpt without data loss????

There are Linux apps to convert, never used them.

But the issue really is that Windows only boots in BIOS boot mode from MBR partitioned drives.
And Windows only boots in UEFI mode from gpt partitioned drives. (and you need newer UEFI hardware).

Ubuntu can boot from gpt with either BIOS or UEFI but with BIOS you must have a 1 or 2MB unformatted partition with the bios_grub flag for BIOS boot or a FAT32 formatted partition as the ESP - efi system partition.

Probably best to fully backup and reinstall if you have newer UEFI hardware.

I started converting to gpt years ago when I still had XP. But XP was on MBR drive with Ubuntu on gpt drive.

Converting to or from GPT
http://www.rodsbooks.com/gdisk/mbr2gpt.html

GPT Advantages (older 2010 but still valid) see post#2 by srs5694:
http://ubuntuforums.org/showthread.php?t=1457901
https://wiki.archlinux.org/index.php...antages_of_GPT
http://en.wikipedia.org/wiki/Unified...ware_Interface