Try using DaVinci Resolve. To replace a background in this program:
Load your video into the timeline (this can be done by dragging the video from the file manager into the timeline)
Click the "Color tab" in the bottom row.
Right click on the video in the node screen.
Under "Window" click the pen icon.
Trace the subject(s).
Click the &...
Aktually Zoom provides this possibility - even in the free version - to:
Convert these to a format that is suitable for presentation in the browser - or alternatively stream the video directly
Use virtual backgrounds, be it still pictures or other prerecorded videos
Even without green screen it's amazing what their smart background feature ...
Do try using the free version of the VSDC video editor that is available from https://www.videosoftdev.com/. I have been using its basic abilities for some months now with excellent results; I have just checked to find that it also does motion graphics.