DARTS Scorer 2021 is the best and most easy to use darts scoring app for all platforms.
You can play X01-games online against your friends and relatives. The amount of online players is unlimited and you don't need to setup accounts. Just tap on "Online", create a game and share the join code. Other players can join to your game using the join code. It is also possible to rejoin the game using this code if you had connection issues. The online-mode supports cross-platform multiplayer with Windows, Android and iOS.