I was finally able to update Flarum — the 1.0 release contained a bug that made the Starling Forum unusable, so we had to wait for the 1.1 release. I just installed that version, and it's running fine so far! However, if anyone notices problems, please tell me about it.
BTW, it seems that the old version showed some problems lately, and emails weren't always sent out correctly. I was able to fix those issues, as well, with the latest version.
And for those of us who are old enough to know about RSS feeds (like myself 😂), the forum can now be monitored with an RSS reader again! The URLs from above are now working again. (The respective plugin was finally updated to the latest Flarum release, too.)
All the best, my friends!