Are you running Parallels or Fusion or some other virtualization software to run Windows (or Linux)? Parallels, for example, can be set to over-ride the default browser (and mail) settings - redirecting such things to a virtual machine's browser ... and the shortcut business wouldn't work in that case.
Can't think of anything else - it should just work. Hopefully someone else has an idea.
Cheers,
Karl
PS I just tested with AC 12 and it works fine for me in Lion. Maybe there is something amiss with START edition...
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB