> What new courses should we add?
The courses you have already are good, but are quite low-level. To broaden the applicability perhaps you could also try something like "build a REST API that matches this OpenAPI schema" (getting persistence working properly could be an interesting challenge). Going further, I wonder if it's possible to do a course like "build a web app that does X" (Realworld or TODOMVC are possible values of X), using browser automation to test. This is probably very hard without manual review. (Scoped broadly enough, this could be solved with a server-rendered framework or a client-side framework.) Common engineering/craftsmanship problems here are authentication, persistence, navigation, performance tuning, perhaps log-wiring, etc.
More generally, I'm wondering if there is a good open-source option as a competitor / baseline comparison? As others have noted, Leetcode is one common source of study exercises, but it's quite annoying to work with as you need to submit code in the browser rather than using your IDE. I'd love to see a repo with exhaustive test cases for the things you're building; for example low-level algorithmic exercises like "exhaustive tests for binary search tree" or higher-level "build a git client" like CodeCrafters offers. Being able to step-debug through failing test cases is always going to be more realistic training than the Leetcode workflow.