Occasionally you may experience feedback in a video call session, this can be caused by your device/settings or the device/settings of the person who you are meeting with.
Feedback can only be caused by one thing: a microphone picking up sound being broadcast by a speaker, amplifying that sound and sending it through the speaker, the mic picking it up again, amplifying it, and so on.
Whatever video call platform you use, the most reliable way to eliminate feedback is by using headphones, since the sound that's coming out can't be picked up by the mic.