Quadrant Next is now available on Windows and Linux.

Here's the link for Windows

Here's the link for Flatpak.

Warning: Flatpak might have login issues, but that's not confirmed/denied yet. I've yet to check this. If you're actively using Quadrant ID, consider waiting before updating. (Last time I was testing Linux there were no issues, but it's really hit or miss with handling protocols through flatpak, you might want to opt for the Fedora/Debian packages or attempt to use the AppImage).