I just finished the Developing Secure Software course from The Linux Foundation.
It was a solid introduction to the basics of developing more secure software. It features a good overview of the tools and techniques that can be applied during all phases of the software development lifeycle. I had a solid understanding of some of the material (e.g., cryptography and GDPR) but it was a good refresher on those topics and got me thinking much more about the process of designing and developing secure software in general.
The most specifically useful information to me was the discussion of the software supply chain. We use many components from third parties and it’s important to think about their origins and how they are integrated. Really good stuff.
The course is free and well worth the time it took to go through the material and the final exam. It’s an important topic and you can’t know too much about how to implement secure systems.