Automatically share WordPress posts on Mastodon. Supports image uploads (and alt text), custom formatting, and so on.
Compatible with the classic as well as the block editor ("Gutenberg").
Share on Mastodon supports 3rd-party WordPress apps, too, on the condition that the "Share Always" setting is enabled. (And, for more fine-grained control, there's a filter hook.)
Share on Mastodon can also be added as a Micropub syndication target, allowing you to enable (or disable) sharing right from your Micropub client. (You'll want to disable "Share Always" for this.)
Simply download the plugin from https://wordpress.org/plugins/share-on-mastodon/ or install from within your WordPress' admin interface.
Complete documentation as well as example code for extending Share on Mastodon can be found on https://jan.boddez.net/wordpress/share-on-mastodon.