Whichever way suits the two of you best, surely? That could be Zoom, Whatsapp, Facebook, email etc. Or if either/both are a bit technophobic, you could even use those good old fashioned methods such as telephone calls or writing letters.
I use the Facebook Messenger App Just the same as using your telephone, but free.
I spend hours talking to my best friend in Spain every week. You can talk face to face as well.