HP Probook 455R G6 laptop if matters....
2 TB nvmne SSD, one 1 TB part Windows 10 with their 4 primary partitions, the rest 1 TB is not allocated. (Windows was cloned from an 1 TB SSD)
Option install alongside Windows goes to shrink the main Windows partition even there is 1 TB free space on disk.
Option something else: pick the free (unallocated) space, set new partition, make it ext4, mount to /...
the installer makes a new 1 MB (!) ext4 partition leaving the rest unallocated. No way to make a new 1 TB partition with the installer.
(I used gparted to make a new 1 TB ext4 partition, so the setup was successful)
HP Probook 455R G6 laptop if matters.... 2 TB nvmne SSD, one 1 TB part Windows 10 with their 4 primary partitions, the rest 1 TB is not allocated. (Windows was cloned from an 1 TB SSD)