Wire mobile apps have been reliable through several years of daily use. Does not require a phone number and Wire is working on interoperability with other E2E messaging services, via the IETF MLS protocol.
I already mentioned in my comment above that when a chat app misbehaves I don't spend time doing that and that my friends are even less likely to. It might seem unfair to you but that's just how it is. If it doesn't work I move on. Best of luck to Wire though.