Hi,
It might be an idea to leave some disk space unallocated as part of the default install options.
Here’s why:
(all of the following is further complicated by LUKS - which is not really optional)
As part of the default install you get Logical Volumes.
Using LVM2 comes with significant additional brain strain (imho / when issues arise etc ) and The main (only?) advantage of LVM for desktop users is that it allows you to make snapshots and thereby take a consistent fs backup without shutting down.
Alas the snapshot space has to be in the same Volume Group as the volume being snapped. So, in the absence of unallocated space, to use a snaphot you either have to shrink /home to make room or add another disk to the VG.
You can’t shrink /home because the default file system xfs does not support shrinking and you have to shrink the fs before you shrink the LV.
Adding another disk where the space is assigned to the VG your system is on and the LVs are part of your system VG and your sytem still boots is … non-trivial.
Unallocated space can be reclaimed relatively easily by the user later if desired as you can grow an xfs and the option to create snapshots out-of-the-box for backups would be useful.
As a side note it is a Testament to how far up my *$ Microsoft are trying to crawl with Windows > 7 that I am persevering with the move to Linux (finally).