I took several Interaction Design Foundation courses online, beginning in February 2020. As high level classes, they focused more on concepts and theory than on specific tools, and they were a great way to refresh old skills and build new ones.
I especially enjoyed the Accessibility class, which raised my level of awareness and helped me make sense of the requirements and tools out there. While I may not always know the best way to solve an accessibility problem, I feel confident in the tools and accessibility testing techniques that I can use to find an answer.