If you're new to Spring Boot and looking for quality learning resources, I've found these bookmarks quite helpful when ramping up people new to this powerful framework.
At just two hours and with no ads, what's not to love about freeCodeCamp's Spring Boot Tutorial?
The JetBrains Reactive Spring Tutorial is a full-featured ten part course. An accompanying YouTube Playlist of the videos is also available alongside the Github repositories and other instructions. This is the first video:
Spring Guides are from the Spring website and cover not only Spring Boot, but also the variety of accompanying libraries in the ecosystem such as Spring Data. They are often focused down to very narrow use cases which is handy when you're trying to figure out how to accomplish a specific task one day.
Baeldung's Learn Spring Boot series is great for developers from beginner to advanced and often serve as good reference material later on as well.
If you are learning Spring Boot, I am also posting relevant content every week at my website! I hope it helps!