As we use the Woltlab Suite Core, we are bound to PHP and use it with the as a FPM. Currently version 7.4 is running on all of our hosts and we use a lot of the recently added typing and nullability features to write more reliable code that can be easier analyzed through our tools.
We also use it for some WSC embedded cron-scheduling and internal web-interfaces, but tend to use a more modern Frontend-Backend architecture for all newly created projects as we enjoy the clear differentiation between View and Controller.