How do I get theme suggestions for a custom block attached via an entity reference field?

Question

I have created a custom block type with the machine name "score_card". I am displaying it on a node page via a paragraph with an entity reference field that references blocks. I would like to get a template suggestion for it along the lines of "block--block_content--score-card.html.twig".

I have template suggestions turned on and I do see suggestions in the HTML output for the paragraph, the reference field and the individual custom block type fields. There are no suggestions shown for blocks at all, not even block.html.twig. Attempting to just place 'block--block_content--score-card.html.twig' or 'block--score-card.html.twig' in my theme has no effect.

I also attempted to generate the theme suggestion using the suggested fix in this thread of adding hook_theme_suggestions_block_alter to no effect. Running this code through the debugger shows that the hook is not called for the block referenced via a field.

Using Drupal 8.9 latest how can I implement a custom theme for a custom block type referenced via a an entity reference field?

Answer 1

I finally got some nice simple template suggestions by using the Block Content Template module. Found it from recent discussion in a core issue. Thanks to all involved.

For example this gives me : block-content--55.html.twig, block-content--hero.html.twig and block-content.html.twig when rendering a block content attached to an entity reference field.