Jitsi.

Element/matrix does indeed have a web version. You can use https://app.element.io, or you can self host the web client.

I think Element does what you’re looking for. Get yourself a fediverse account, log in and watch it go. Difficulty, as ever, is getting your contacts to switch.

matrix has a web interface and there’s many different options for clients. https://matrix.org/ecosystem/clients/

there’s also signal but idk if that will suit your needs

there is revolt that is like discord but it is open source. downside is it is not e2ee

E2EE with a server web interface is a technical impossibility. The ends are the clients. By definition the server is only there to pass encrypted data from client to client. Presumably you can make this work with a web client using the browser’s local storage, but at that point you’re not actually looking at a web site and you might as well just use the official app. This is one reason why Telegram doesn’t do encryption by default: group chats are particularly hard to do with EE2E.