> Not sure I follow. What's the problem here? The advantage of static linking here will be to not have a dependency on the shared object, which can be quite beneficial.

The problem is that some features are not baked into the .a files. They are always provided as shared libraries. This included OpenSSL engine extensions such as AFALG engine or external engines like p11-kit, OpenSC, or others. OpenSSL 3.0.0 moves some features into external OSSL provider libraries, for example legacy crypto algorithms. I have not figured out how much functionality we woud loose without engines and external OSSL providers. https://www.openssl.org/docs/manmaster/man3/OSSL_PROVIDER.html
# 3.0.0 alpha build:
$ find -name '*.so'
./engines-3/padlock.so
./engines-3/capi.so
./engines-3/afalg.so
./ossl-modules/fips.so
./ossl-modules/legacy.so
./libssl.so
./libcrypto.so