See the postfix notes.
The next version of OpenSSL will be 3.0.0. Version 1.1.1 will be supported until 2023-09-11 (LTS). Version 1.1.0 will be supported until 2019-09-11. Version 1.0.2 will be supported until 2019-12-31 (LTS). Version 1.0.1 is no longer supported. Version 1.0.0 is no longer supported. Version 0.9.8 is no longer supported.
A big question is what current Linux LTS distros support