OpenSSL won’t have access to iOS’ built-in keychain which will cause cert validation issues. It will take more time to determine the most satisfactory path to travel from here, but easiest workaround for development purposes will be to turn off cert validation.
If you must have cert validation immediately, then you could either use Mozilla’s cacert.pem or extract the keychain store from the mac itself using something along the lines of https://github.com/Homebrew/homebrew/blob/00afa52c222ea97b0e15e8aed315f6eb8aa922b9/Library/Formula/openssl.rb#L71. Then, you could switch using the default paths to using this file.
If you must have cert validation immediately, then you could either use Mozilla’s cacert.pem or extract the keychain store from the mac itself using something along the lines of https://github.com/Homebrew/homebrew/blob/00afa52c222ea97b0e15e8aed315f6eb8aa922b9/Library/Formula/openssl.rb#L71. Then, you could switch using the default paths to using this file.