Besides the obvious (the material by Robert C. Martin), what are some other good resources for learning about clean architecture?

I found that this talk by Ian Cooper overs a good overview:

DevTernity 2019: Ian Cooper – The Clean Architecture

If you want something that you can apply to TypeScript, you might want to check out the SOLID book by Khalil Stemmer.
You can also check out his blog, for example, the article about Comparison of Domain-Driven Design and Clean Architecture Concepts.

There’s also another book called Get Your Hands Dirty on Clean Architecture by Tom Hombergs which looks promising.
For a glimpse at the content, you can read the article Hexagonal Architecture with Java and Spring.

Further Reading