Since there was not a specific area of interest mentioned, I'll provide some general recommendations. These are what I found to work well for me.
I second @williaml post - and like to add that there is a video course available called Data Science with R.
general recommendations
For beginners - introduction to many different topics in R:
Awesome guides by RStudio
There are many books available, for free! Nearly any subject, written by wide range of specialists.
Both the recommendations mentioned above can be found here, as well as hundreds of other interesting reads.
Awesome collection of books.
Another thing I personally found extremely helpful is to follow some TidyTuesday content creators, to learn new approaches.
Conferences
Think of a use case, and there is likely a package of functions dedicated to it, with detailed documentation and enthusiastic developers supporting it. Conferences provide a great way to learn of new packages and stay up-to-date on best practices.
Some package recommendations
learnr - to gain access to interactive tutorials within RStudio IDE.
swirl - to gain a story-like introduction to many concepts at the command line.
reprex - for asking questions when you encounter hurdles
To find packages for a specific use case, consider
CRAN task views
BioConductor likely has a similar feature, but I don't know it.
personal recommendations
A mindset (in my opinion) is most important when learning R.
- Having a use case. Something that challenges you.
- Find recent material. R has been around for a while. Many blog posts, tutorials etc. are outdated.
- "Could this be done in R?" I found it helpful to every now and then think of tasks or concepts I encounter in day-to-day tasks and relate them to R. How would I implement them? A manual way to do this is to browse through things like Leetcode problem set, for which no definitive answer yet exists.
- Find how others have solved problems. Stackoverflow - RBloggers et cetera.