It seems like the recent changes limit was recently lowered to 1000 (down from 5000). 1000 has been a limit in the select box for a while now, but changing the limit parameter in the URL would work for up to 5000. Since 24 to 48 hours ago, this behavior has changed and I believe wrongly so. I've been relying on that feature for years now, so that I could reach into more distant past in the recent changes. I've noticed this problem on srwiki.
e.g. https://sr.wikipedia.org/w/index.php?limit=1000&title=Special:RecentChanges and https://sr.wikipedia.org/w/index.php?limit=1500&title=Special:RecentChanges return the same list of recent changes (the latter is not longer, as expected)
This might be related to T172026#3483291