I found the link to 2.9.9.9.4 so my site is repaired.
The only question that remains is: Did today’s update break compatibility with PHP 7.3 on purpose, or was it an accident?
I now have a suspicion that my PHP version is too old.
Is it possible to download the previous version of the plugin, until my server can be upgraded?
I’ve looked, but can only find links to verson 2.9.9.5.5