Downloaded https://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/11.3.0-live+nonfree/amd64/bt-hybrid/debian-live-11.3.0-amd64-mate+nonfree.iso.torrent and copied the iso to a usb key. Fired it up and selected install. When asked about language chose to go back and then perform check integrity, which gave a lovely red screen with "No valid Debian installation media".

Repeated copying to usb key and integrity check, same result.

Can you confirm a problem with the iso?

(Did I get the package and version right?)