In the stable repo, but there are backports, testing and unstable repos too, if you want later versions and accept more risk of bugs.

Trac has backlog and milestones (for epics and sagas) and plugins offer kanbans. It’s been OK when I’ve used it, including hosting one.

Didn’t nextcloud fork from that because reasons?

edit to add: no, that was ownCloud. You are in a twisty maze of project names, all different.

Check your autorenewal failure alerts go somewhere you’ll react to.

That depends who’s hosting it. There’s few good reviews of email hosting out there at the moment.

Even if you self-host, other people’s mailservers still interact with it, unless you only chat with other users you host. And some of the big webmails variously get really pernickity about your DNS, DKIM and more, or they deploy some pretty obnoxious countermeasures against your server with little explanation. So I’d say it’s more often both than not, no matter what you do. If you think it’s not being a pain, there’s probably an unpleasant surprise in your server logs or coming soon!

It’s still often worth self-hosting, but that’s more big webmail really sucks, even ISPs often don’t set their mailservers up well and it’s often an early casualty of ISP managers looking for costs to cut.

Those apt commands are in a less-good order. It’s usually better to update apt, then upgrade the system.

I upgrade as soon as reasonably possible after the notification appears, if the system isn’t on auto-upgrade.