I circumvented that problem by creating a /discworld partition and putting my personal stuff in there. During a reinstall I MOUNT and not format /discworld. 2 disks I use: a ssd for / and a hdd for /discworld.
My /home is void of anything personal and is part of / and not a separate partition.
You can use How to create partition for data? as a reference and create your own partition (add a volume label!).
You then might need to shrink /home/ and enlarge this partition.
You can use How to resize partitions? as a reference.
Then copy the directories in /home/$USER/ over to this new partition and edit ~.config/user-dirs.dirs to point to the new partition (keep a backup of this file on that partition so you can copy it back when you reinstall again) and if this all works remove the directories in /home/$USER/.
No more issues in the future: Use a live session for reinstalling and during the partition part remove / and /home and MOUNT your data partition (be careful here: pick the correct one; remember the volume label added when you created it).
After installation copy the backup of user-dirs.dirs to ~.config/user-dirs.dirs and press F5 on the desktop to refresh.
extra: also ditch the swap partition. We nowadays use swapfile so we do not need to do anything for that anymore.