Duo doesn't require a Google account. From the article:

> Duo is simple from start to finish. To get started, all you need is your phone number and you’ll be able to reach people in your phone’s contacts list. No separate account is required, so you can sign up in just a few steps.

Some searching yielded https://appear.in/

(I'm not affiliated with that website)

Appear.in is great, but like all the other WebRTC chat services, you still need to use another method of communication to notify the other part(y/ies) of the call either by phone, SMS, IM, email, IRC etc. so they can then click the link to your chat and grant their browser permission to use their mic and/or camera, IF their browser is up-to-date enough, and not Safari. ... That's what makes these otherwise perfect services suboptimal for the majority of non-techies.

Which by the way works very well for our daily meetings.

I had suggested Wire [1] in a comment above [2]. It's cross platform, has cross device sync, and end-to-end encryption. Sign up can be using the phone number or an email address.

[1]: https://www.wire.com

[2]: https://news.ycombinator.com/item?id=12296477

You could try Viber, it requires a phone number login though.

I think there is something called imo in which video conferencing works in 2G network

Why the down vote? There actually is an app called "imo" which does both text and video chat in skew speed network