With 8.1 and latest libmongocrypt, there is support for $lookup in CSFLE and QE with field level encryption. We need to add at least a mongosh e2e test that uses the latest libmongocrypt (already updated) and crypt_shared (will be available after 8.1 release). 

This has already been manually verified with https://gist.github.com/addaleax/4c2701cf877fbaaf92e9cf5861639608 using a development build and we can use a development build for the E2E as needed.