This isn't what Fossil does.

Fossil lets you synchronize artifacts both ways, so you can clone a repo, participate in discussions when on a plane, write some replies, connect back to the internet and sync them back up to the server.

When your server goes down, you don't lose anything. There's no need to remember to back up your issues every day, every time you clone the repo, you also clone its tickets, forum, wiki etc.

Fossil doesn't have a good story around cross-repo authentication (without separate per-repo accounts), CI/CD, 2FA, SSO support and such. It's a great tool if you're writing a single personal project with little regard for security, but that's about it.