This is a good question: submitting a bug report should be feasible without maintaining an account at GitHub (other issue trackers manage it just fine with only existing email communication, for example).
Unfortunately, GitHub, like so many other centralised platforms that assume they’re the centre of the world, expects you to create and maintain a personal identity special to GitHub, in order to submit a bug report at all.
This is a good question: submitting a bug report should be feasible without maintaining an account at GitHub (other issue trackers manage it just fine with only existing email communication, for example).
Unfortunately, GitHub, like so many other centralised platforms that assume they’re the centre of the world, expects you to create and maintain a personal identity special to GitHub, in order to submit a bug report at all.