HAOS doesn't really share. It's a full Linux distribution designed to be the entire OS on whatever it's installed on, and it runs its own internal containers through the Supervisor. The Supervised install, the old middle route, is no longer supported (its end of support was release 2025.12).

So on one Pi 5 you pick. Keep HAOS and live with what runs as an app there, which is what add-ons are called now. Or put a regular Linux install with Docker on it and run the official Home Assistant Container image next to the arr stack, Deluge and Jellyfin. That's the whole trade. Container has no Supervisor, no apps and no one-click updates, so anything you run as an add-on today becomes its own container, and Thread and Z-Wave, which run as apps, get no out-of-the-box support. Either way, take the full backup first, as uten151 says, and I'd do the SSD move soon: Home Assistant's own database writes can wear out an SD card.