A Supervisor's Perspective ...
Normally it is ethically required that therapists work strictly within their competence. We would normally expect that therapists who are new to online or phone therapy would first acquire competence through training. There are, of course, therapists who are trained in online and phone therapy. However, we are in extraordinary times and therapists may have conflicting responsibilities: the responsibility to continue to provide "holding" for vulnerable clients versus the responsibility to assess and work within their competence. It seems to me that the times call for therapists to assess client need and where continued therapeutic "holding" is required, therapists may need to provide it to clients through means other than face-to-face. What each therapist will need to do is assess what is within their competence in online or phone therapy. This may not be full-on psychotherapy and may have a "holding and supporting" function instead.
Apart from the obvious technical issues, there are pitfalls in online and phone therapy. One key issue is that clients often drop their filters in online contexts and may reveal much more than they would intend in a face-to-face session. Where clients are moving from face-to-face work to online/phone sessions, this issue may need to be addressed by client and therapist.
Clients use online and phone communications for informal communication purposes and this can filter into sessions, with the client inclined to much more unboundaried informality that is the case in face-to-face sessions. The therapist needs to hold the boundaries and to keep the frame in place. This may mean passing on the client's offer to take the therapist on a virtual tour of the house and garden, or to meet grandma resting in her sitting room armchair!
It seems to me that therapists who are new to video sessions may not realize the need to look around and see what their camera sees inside their own home - the camera sees things that familiarity causes us to no longer see. A student friend of mine recently took part in an online lecture from the lecturer's home. The students asked to see the lecturer's cat who could be heard in the background - the lecturer turned the camera towards the cat only to accidentally include a distant shot of her teenage bed-headed son, who was not amused! The familiar things of home probably shouldn't appear in camera shots? Trick of the trade for online video sessions: check what is seen in your own camera BEFORE you start.
A Case in point ....
IPersonally - I am using Duo for Video calls and mobile-to-mobile for voice calls to clients for psychotherapy and supervision. It is a very different experience from offering supervision and therapy is my own therapy room. My room is a creative ally to the processes of therapy. Without the safe and creative haven of the familiar therapy space, I am having to adapt and adjust along with my clients - together we seem to be getting there, as if a different therapy room is forming.