I’m not sure what you mean by “dynamic avatar”. Maybe this is when a user creates their profile but they do not upload their picture. In this case, we can give them a default avatar.
One method: use the “generate image” column and set this as the image in the user profile.
Another method: see the topic where @Robert_Petitto explains how he generates dynamic avatars.
I possibly totally misunderstood your question, if so my apologies.