Hi Kevin, Rhasspy does indeed work with RPi4 hardware. Both as a Home Assistant OS add-on, or stand-alone on Raspberry Pi OS. The Rhasspy documentation gives instructions for both (in different sections) but I felt it could have been clearer about which is better for the different scenarios.
It looks as though you have installed Home Assistant OS on the RPi, and you have “Rhasspy Assistant” in the Supervisor > Dashboard. That’s good.
On the Rhasspy Assistant page, did you go to the “Configuration” tab and select your audio hardware ? This is where i personally became unstuck because my microphone hardware (respeaker hat) wasn’t listed. But this is a separate issue, and we can come back to this later if necessary.
I assume you have clicked “START” on the Rhasspy Assistant’s INFO tab; and get the error when you click the “OPEN WEB UI” link ?
The Rhasspy add-on runs in a separate Docker container, and the Http 500 error is a web server problem, so I suspect the Rhasspy add-on isn’t running properly.
Go to the Rhasspy Assistant’s LOG tab and paste the log here.
Have you rebooted Home Assistant since installing Rhasspy (Supervisor > System tab > Reboot Host) ? If not, it might be worth a try