Github dislikes email “aliases” so much that they will shadow ban your otherwise normal activities for months, and once flagged, support will request not only a “valid” email domain but also that you remove the “alias” email from the account completely.
This isn’t to say every project should self-host, but that they could self-host. And if you don’t want to self-host, you can join groups like Notabug, or a server hosted by a foundation like Codeberg, or the privately-held SourceHut, or even the open-core GitLab with its free tier (tho publicly-traded, most of the source is open & one can run the community edition if they wish). To assume if not self-hosted GitLab CE, then one must use a closed-source, US-based, publicly-traded, megacorporate, social media + code forge platform that’s trying to monopolize the developer tooling space is a false dichotomy.