Question: What do I do if I find a bug?
Answer: Let someone who may be able to help know about it.
There are many steps involved in reporting a bug such that others can reproduce it and then fix it. Your first port of call might be the WordPress support forums.
If you know the problem is in the Gutenberg plugin or a new FSE theme then you may want to raise an Issue on the appropriate GitHub repository. Before raising the issue, check it’s not already a known problem. It’s a laborious process, which is why it’s a good idea to get someone to help you.
You can report bugs on the documentation as well as the code.