The most appropriate alternative to Skype is just renaming it to Teams (everyone is reachable on Teams in the same way they were on Skype).
If you’d rather have WhatsApp, the best thing to do is just create a new WhatsApp field and let people populate that if they want to.
XenForo no longer ships any contact fields by default. New installs don’t have any of the old ones we used to add (no Skype, Twitter or Facebook) and we aren’t planning to add new ones at this point.