I second the sharpen prompt, and the UX design course with Google. Or https://designercize.com/ will give you random prompts to work on. Source: over 1 year ago

For basic topics you can look at CollectUI's subjects and pick some that interest you. For more advanced subjects I can recommend Designercize. Source: about 2 years ago

Actually just stumbled upon https://designercize.com/ myself today and did a few prompts with my boss. The randomness helped push me to think outside the box and find more reasonable (albeit absurd) solutions. Source: about 2 years ago

I need to practice my whiteboard challenge skills. Anyone wants to do this with me? We can get prompts from these places: https://designercize.com/ or https://sharpen.design/ and come up with things on zoom. Source: over 2 years ago

Designercize.com, if you look to solve whiteboarding challenges that might be happen as part of hiring interview process. Source: over 2 years ago

Did you try 'UI design patterns' as your search? There are some websites there that list common and not-so-common takes. Source: over 1 year ago

I'd suggest you sign up on UXArchive and search your favourite apps or take any app. Download the files it provides and try to recreate the same screen on Figma. Source: about 2 years ago