A migration guide is being worked on in https://github.com/openssl/openssl/pull/14710
You might want to provide feedback with comments there to help making sure useful information is not left out.
Nicola
P. S. It's a pity that a lot of external resources, including blog post, articles and stack overflow q/a are still referring to RSA_* and similar low level APIs that have been more or less informally deprecated for some time (more than 5 years), without nobody really caring as long as it was a deprecation only on the documentation without compiler warnings. We do need a community effort to make sure top results in web searches stop suggesting outdated code snippets. The efforts on this migration guide and on the demo applications is a step in the right direction.
