Winchil RV&S 12.3 supports Matlab 2019b?

You probably want to post this question in this RV&S (Integrity) specific forum:

https://community.ptc.com/t5/Windchill-Systems-Software/bd-p/Integrity

I believe there are plans to support 2019b come RV&S (Integrity) 12.4, but someone in that forum may have better idea, or you can open a Support case.