I think it may make sense to use a combination of two things.
For persistent text chat with all the trimmings and more, I'd recommend Zulip, which is Open Source, and which you can either self-host or have Zulip host for you; because it's open, you can always move from the latter to the former as needed.
For audio, video, and screen sharing, I think Jitsi is the best available option at the moment. That is *also* Open Source and supports either self-hosting or having them host it for you. And it's integrated with Zulip, so you can hit one button in Zulip and get a voice or video call people can join.
For persistent text chat with all the trimmings and more, I'd recommend Zulip, which is Open Source, and which you can either self-host or have Zulip host for you; because it's open, you can always move from the latter to the former as needed.
For audio, video, and screen sharing, I think Jitsi is the best available option at the moment. That is *also* Open Source and supports either self-hosting or having them host it for you. And it's integrated with Zulip, so you can hit one button in Zulip and get a voice or video call people can join.