It does not mean total data loss. I have updated from Android 7 / Nougat builds right up to Android 13 / S and have never lost data.
It’s quite straightforward:
- Back up your Q data
- Dirty flash the upgrade
- If it doesn’t boot, format your data partition
- Clean flash the upgrade
- Boot and go through first time setup
- Restore your Q data
You can back up EITHER
- using TWRP as described here.
- OR using Android Backup and Restore Tools project
More information on both methods here