How to encrypt with RSA programmatically

OpenSSL 3.0 provides the following APIs for RSA encryption:

• A legacy API with the RSA_ prefix and the RSA_public_encrypt() function. This API has been deprecated since OpenSSL 3.0, so we are not going to use it.
• The EVP_PKEY API, particularly the EVP_PKEY_encrypt() function. We are going to use this API.
• The EVP_Seal API. This is a hybrid encryption API that generates a session key, encrypts the session key with RSA, and then encrypts the user data with the session key. This API contains the EVP_SealInit(), EVP_SealUpdate(), and EVP_SealFinal() functions, which work similarly to EVP_EncryptInit(), EVP_EncryptUpdate(), and EVP_EncryptFinal(). EVP_SealUpdate() is just #define for EVP_EncryptUpdate(). There are also the corresponding EVP_Open functions for decrypting the seals – EVP_OpenInit(), EVP_OpenUpdate(), and EVP_OpenFinal(). Unfortunately, the EVP_Seal API is rather inflexible. It supports only RSA encryption of...