Nintendo Switch Online is described as 'lets you connect and communicate with others on Nintendo Switch™. Invite friends to play with you via social media, and use voice chat while gaming' and is an app in the Gaming Software category. There are 2 alternatives to Nintendo Switch Online for Online / Web-based, Playstation, Windows and Xbox. The best alternative is PlayStation Network, which is free.
PlayStation Network, often abbreviated as PSN, is an online multiplayer gaming and digital media delivery service provided/run by Sony Computer Entertainment for use with the PlayStation 3 and PlayStation Portable video game consoles.
Xbox Live (Silver) is free for basic features such as messaging and dashboard and game updates. Xbox Live Gold (paid subscription **) is required for match making and may be required for other game functionality over the internet. The most advanced multiplayer.