I can offer a variety of different options:
Whereby.com
A video conferencing room that can do individual sessions or a group of up to four people; it has end to end encryption, complies with GDPR, is a locked room with a waiting room facility so no-one can enter the room uninvited. There is no need for an app as the room details can be typed into your internet browser.
Doxy.me
A video telemedicine platform for one to one sessions; this has end to end encryption and also has a waiting room facility. Again there is no need for an app as the room details can be typed into your internet browser.
Zoom
A video conferencing platform that can do individual or group sessions; At present Zoom does not have end to end encryption and it appears that sessions are held on Zoom servers (so I cannot guarantee total confidentiality). However, I do set privacy settings to avoid Zoom-bombing including: one time only meeting ID's with passwords (I send a new meeting link each week via email); a waiting room facility; and once the session starts I set the 'lock room' function.
Whatsapp video calling
Telephone sessions