I had no choice. Support for Joomla 3 is coming to an end, and we cannot live with a content management system that no longer receives security updates.
So slowly, slowly, I went through all my Joomla Web sites (I have several) and updated them to Joomla 4. It was a painful process. The template I use for visual presentation is old (I know, I know, but that's a project for another day.) There were incompatibilities.
Also, back in those more innocent days when I began using Joomla (version 1.5!) I grabbed a few useful extensions in the hope that they'd make my life easier. They did... for a while. But eventually they turned into liabilities. Many of them are no longer maintained, and often, there are serious incompatibilities with Joomla 4. So I had to get rid of them, either rewriting pages to no longer rely on the component, or creating a replacement component myself.
Long story short, my Web site is now fully functional in the test environment where I am writing these words. If all goes well, within minutes I should be able to install this in the production environment as well. We shall see how it goes.