We also found that yesterday. Sorry, it seems that 4.23 is not possible to compile the whole engine with RTTI on (which is not supported anyway). If you need RTTI for a specific third party module only maybe you can enable it just for that one? You will need a shim module to communicate with that third party lib (similarly to OpenExrWrapper module)
EDIT: if you still want to compile the whole engine with RTTI you will need to either disable or rebuild WebRTC. You can disable it by editing XMPP.Build.cs and setting TargetPlatformSupportsJingle = false for Linux