To install a new version while maintaining your current separate /home partition, you need to select "Something else" between the options that the installer presents.
That brings you to a screen where you can designate mount points for the new installation yourself.
In that screen, assign your current root partition (
/) to become the root partition of the new installation. To that aim, you click the partition. You then get an "Edit partition" dialog:
There you indicate how the partition must be formatted ("use as"), whether the partition must be formatted or not, and where the partition must be mounted.
- For the partition you currently use as root partition: Use as: ext4; Format: Yes; Mount point:
- For the partition you currently use as home partition: Use as: ext4 (provided it is currently in ext4); Format: No; Mount point:
If you continue the installation, the root partition will be fully wiped. The files on the '/home' partition will be preserved.