VS2019 isn’t officially supported yet (to my knowledge). Also, make sure you use the version that Epic’s build farm uses. While it’s tempting to always be on the latest version of VS, it will cause compile issues like this. Even small updates x.x.3 -> x.x.4 can cause no end of headaches.
You can try and add the error (C4800) to the list of ignored errors in the .build.cs files, but other than that - you may be hosed and should drop down to VS2017 if possible.
From the 4.24 Release Notes: