Porting to LibreSSL

Hello, I use LibreSSL on my Linux system. In most cases it's possible to find patches to keep things building with it, but in some cases I'm waiting on patches that will never come. Just hit a roadblock with version 4 of the Lean theorem prover which is locked to OpenSSL 3.0. Unfortunately the SSL API is pretty complex, and I don't understand it well enough to write my own patches. Is there some kind of porting guide available which explains differences between each version of the LibreSSL and OpenSSL APIs? 

Thanks,
Dave