I just spent the day (and then some) upgrading both the development version of this site and this site, and it has not been a fun upgrade. Part of the problem was that I had to switch themes, as the d8_blog_theme has apparently stopped being maintained. But thanks to my friend Dave, who does Drupal professionally, he cloned the repo and did some fixes in addition to making it compatible with Drupal 11. But I had to stop using the old theme, uninstall and clean up some themes, and do some other steps to get the functionality I had configured into my site, such as the background image.
I also had to go through the process of upgrading both of the PostgreSQL servers for these sites from 13 to 16, and on RHEL, the old version is completely overwritten by the new version, so rather than doing a pg_upgrade like normal, I had to do an initdb and restore from SQL dumps. Thank goodness for VM snapshots, because I had to rollback to the snapshot I took from before the upgrades.
So now everything is at the latest and greatest, and Drupal will stop hounding me that there are available updates because one module had an update which was incompatible with D10.