FreeConferenceCall.com has long provided free audio calls, but also offers completely free video conferencing, with a pay what you choose pricing model.

• The completely free version offers unlimited minutes of talk time for up to 1,000 participants
• Visit https://freeconferencecall.com for more details

To avoid being hijacked (Zoom-jacked) during a meeting there are a few precautions you'll want to take to minimize that risk

• configure only the Host to share their screen (you can easily make some of the participants co-hosts, if you want them to share their screens)
• require registration of attendees prior to the meeting
• use a waiting room, that allows you to only admit registered Democrats to the meeting