Luckily there are a lot of cheap STUN/TURN services out there, and if you really need something under your control, there are containerized projects on GH that make it easy to run your own. Though even when I used it as a Zoom replacement for meetings, I never ran into a situation where TURN was necessary, and that includes people behind corporate firewalls. It seems as though corporate netops learned some lessons during the pandemic and loosened restrictions.