Linux Shout published three ways to install .NET 6 (dotnet) core on Debian 11 Bullseye.
3 Ways to install .NET 6 (dotnet) core on Debian 11 Bullseye
Add the Dotnet Microsoft repository or use Script or SNAP to install .Net Core SDK and Runtime on Debian 11 Bullseye Linux using Command line
3 Ways to install .NET 6 (dotnet) core on Debian 11 Bullseye