There used to be on Android, it's called Disa, but a lot of services actively combat third party clients. It was nice when I used it back in like 2014 because

There used to be on Android, it's called Disa, but a lot of services actively combat third party clients. It was nice when I used it back in like 2014 because if WhatsApp went down I could just keep talking to the same person via Telegram (assuming they had both) and it'd all be in 1 joined conversation.