I installed the WP Downgrade plugin to return to 5.5.3. However, my WP dashboard says I’m running 5.6.1 (I disabled auto update after the 5.6 fiasco).
What’s funny is I have two WP installations on essentially two websites (the issue is on a subdomain and the database is separate from the primary domain). On the primary domain, everything works just fine. On the subdomain – the featured image portion just will not load in the block editor.
I use the subdomain to serve several clients and right now is our busy time of year so taking the site down to upgrade to 5.6.1 to see if the issue is resolved and whatnot is not exactly something I can do at the moment.
I installed the jQuery Migrate tool as well and wouldn’t you know – no issues! So after about a month of running it, I got tired of the messages and uninstalled it.
My feeling (and I’m very, very far from being an expert) is that there is an issue in the jQuery database since WP was using such an outdated version. Seems like the project was rushed to meet a deadline or for some other reason. Either way, WP’s complete disregard for the issue and instead just blaming the end user (it’s so easy to do) is rather disappointing. I get they’re volunteers but seriously – this is a native to Gutenberg and the default editor. I don’t run a plugin that affects how the editor functions just the native block editor that comes with every install of WP. And yet, alas, I’m getting the blame.