Since WordPress 5.8, the Widgets panel has been replaced with new Blocks Based Widgets Panel. WordPress includes a universal Legacy Widget Block that can wrap the normal/legacy widgets for use inside the block editor.
With the WordPress 5.8 release last week, and the new Block Editor based Widgets panel, most plugins with widgets were broken. I have already released multiple plugin updates last week, and today all bbPress plugins with widgets are updated.
After many delays and issues, the Widgets Panel has been replaced by the block editor in the new WordPress 5.8. While I like the idea, the final execution is mostly done badly and will (and already is) cause many problems to countless websites unaware of the changes.
WordPress 5.8 has been released, bringing some major changes that will affect almost every existing plugin, and I imagine, it will break quite a few of them, mostly because of the new block-based replacement Widgets page.