In trixie, libasound2 exists as a virtual package (ie. libasound2t64 provides libasound2) so this ought not be a problem.

It should definitely work with an 'apt install firefox' from the cli - perhaps you're using a different package management frontend? If so, installing libasound2t64 first should force it to see the virtual package - but it might be worth filing a bug report as this really shouldn't require manual intervention...