I use Linux and came back after a while, but I just found out that I cannot play the game any more, because only Windows, Mac, iOS, and Android versions of the game are available.

If it's feasible and maintainable, keeping a browser version would enable people to play on unsupported OSs. It would also allow people to play in situations where they cannot/don't want to install an app (e.g. on other people's computers, when low on space, etc.)