Hi Chris and thank you for your interest in HexOS. You can definitely adapt your current setup to HexOS without having to destroy your existing data. HexOS is based on TrueNAS SCALE, so importing your existing ZFS pools won't be a problem. Here's my recommendation if you decide to purchase:
1) Backup your existing TrueNAS SCALE configuration: navigate to System -> Advanced Settings and download your configuration file as shown in the screenshot below:
2) Reinstall HexOS on your boot drive using our installation media.
3) After rebooting, navigate to deck.hexos.com to claim your server (keep in mind, you'll need to purchase a license to do this), and when you get to the storage configuration part, click "skip".
4) If you have other customizations you've made to the configuration of your system that aren't showing up, you can navigate to the TrueNAS UI again and restore the configuration file you backed up previously.
Let us know if you have any additional questions and thanks for considering HexOS!