Signal's stance on third party clients is so disappointing. Telegram really has them beat there, although it has to be pointed out that Signal actually publishes server source, while Telegram doesn't.
Well,signal doesn't do it always as well, see the 1 year pause when they added cryptocurrency stuff
As a result, you have a large set of very good clients for pretty much all platforms.
Imagine if the FLOSS darlings like Signal would make something as amazing as this - a library any plaform (from RPi, watches, etc.) to implement the best possible secure client that fits the user.