I have Home Assistant:
Installation method Home Assistant OS
Core 2026.2.2
Supervisor 2026.02.1
Operating System 17.1
Frontend 20260128.6
... and I've been trying to install HACS for ages. It would redirect from the HACS site, to my Home Assistant instance, but continually say it couldn't find the app.
Lots of web matches said you could run the get.hacs.xyz script through shell, but didn't recommend it for OS version of HA.
I noticed the repository in the HACS site in the URL being passed to my HA instance was:
... so I went to my HA settings, went to Apps, went to Install App, went to the meatball menu in the top right, selected Repositories, and then added the above URL.
I then went back to the HACS website, used the add link, and it found the app!