Thank you very much for replying.
I am still facing the issue with a clean install of WP 2019 theme + no plugins on a local environment using Flywheel.
Safari will occasionally show the code. Less than 50% of the time. iPhone Chrome/Safari did not show the code. On mobile first load the pre text quickly appeared without any formatting, and then disappeared.
Mac Chrome and Firefox showed the code correctly on load.
Screenshots
