Show telephone symbol in Calendar when using arbitrary video conferencing tools
The only thing you can control easily is be sure the links to your meetings are attached to the event.
This very handy interface came to my attention using Fantastical and it’s super useful, and I’m also waiting for first party support of some handy conference apps.

https://flexibits.com/fantastical

I’m not smart enough (yet) to figure how to format other links that Apple doesn’t now detect, but know you could try another calendar while everyone figures out the exact mechanism to influence this if the vendor apps don’t get updated to claim their links in a manner Apple can connect the event to the helper app.
Here’s the list of what apps fantastical can detect:

https://flexibits.com/fantastical#conference-calls-section