DuckDuckGo runs a free XMPP server - https://duck.co/blog/post/4/xmpp-services-at-duckduckgo
When it goes down, it goes down for multiple days, even a week. Prolonged outages have happened twice or thrice in the last two years, with no helpful messages from the staff. Heck, they didn't even bother announcing the outage before I posted on their community forums.
Their server stopped pushing offline messages to clients a long time ago. People complained, it still doesn't work on my end.
They said they would look into creating a status page, but we still can't tell during an outage if they know about it or not.
The bottom line is that maintaining their XMPP server is simply not a priority for them.
You should look into other providers that use better servers, and are also interested in maintaining their node.
EDIT: I'm basically asking you people to recommend a better XMPP node, somewhere you've personally had a good experience over a long period of time.
While nowadays most of my contacts are on private XMPP servers, I remember few having some reasonably solid experiences with https://jabber.at/ (can be also found at https://xmpp.zone/ for a better sounding domain name, which I guess matters to people who hate the now obsolete "Jabber" term). Can't from my personal experience vouch for a "good for a long period of time", but if someone is looking for at least a well established server, this should be as good start as any. Also, the news page shows they're quite serious about server updates and transparent, which is a big thumb up in my eyes.
Edit: typos