Upgrade while keeping home partition

When you fresh install Ubuntu you have to manually manage partitions. You can decide where to mount / (root) and format that partition, then you select where to mount your home and choose to not format that partition (you don't check the format option). In this way you don't lose anything even if some configuration folder (.mozilla for example) may change. I suggest to backup Home folder before, in case of errors you can remedy.

Here there's a good tutorial.

this is possible.

When you arrive at the hardrive information section of the installer, ensure you select the option to configure partitions manually.

Ensure the partition that contains your home folder is not marked for formatting. You can then manually set its mount point as /home.

The rest of the system will be installed as normal on the remaining partition.