Over my years of online tutoring, I have used most online platforms. This includes Zoom, Skype, WeChat and even WhatsApp video calls, depending on the needs and technical preferences of the client.
My personal preference is for Zoom, due to the Annotate function (to use the platform as an online whiteboard). But I am happy to use another platform if the tutee finds it more intuitive.
When appropriate I will also suggest collaborate with the student over www.bitpaper.io/  (an online saveable whiteboard) and Google Sheets (if planning a revision schedule).