I'm not an ffmpeg maintainer, but it's actually not as hard as you think. You know how when you get an email it shows up in your list of emails? That's your list of issues.

You know how when you get a reply to an email, all email clients that aren't the most absolutely basic will put the original emails and its replies into a thread together? That's the conversation about an issue, in context, with threading.

You know how emails can have attachments? That's attachments. You can put screenshots in there, or patches, lots of stuff.

Now you may be wondering, that sounds like a lot of emails. That's true! But most people who live the mailing list life have filters and stuff setup to expect a lot of unsolicited emails. Like there are headers in the emails from mailing lists that tell you which list it was from, so it's really trivial to have a thing that puts all mail from this list into a folder or something and then not notify on emails in that folder. So, like an issue page, you can check it periodically, maybe mark certain ones as notification worthy, and ignore the rest.

The main upside to this is that the theoretical barrier to entry is relatively low, because every human who has touched a computer basically has an email. And you can have ultimate control of your experience because really it's all about what features your mail client has. And even if the mailing list server goes down you won't get any new emails, but you already have all the emails you've received before, so it's distributed! And you can still send replies while it's down, and they'll just spool until things come back up. Magic!

The main downside is that the practical barrier to entry is relatively high because people aren't used to joining mailing lists and aren't setup for it, and so it ironically feels like a much bigger deal, if you're any "normal" kind of email user, than creating a new username and password account. So for casual users, it's kind of a nightmare.

Also, because mailing lists are usually public, it's really easy to make a web frontend that contains the archive for non-subscribers and search engines and stuff, but while these could look like anything, in practice they look like ass, because mailing list people don't really care about what web stuff looks like a lot of the time. Which makes sense, they're not looking at the web frontend, they're ssh'd into a jump box using mutt through screen, or some set of emacs plugins 😛