I'm currently trying to build a player base for a multiplayer game I've created and I'm struggling to get players. I've tried various ways of marketing but while some are quite effective for players to try the game it usually results in that they try it one by one and rarely multiple people at the same time.

Things I've tried:

- created a web version of the game (this was essential as almost nobody downloads the native apps - but perhaps it is specific to my game)

- I'm trying to be online when others plays (I have a notification when people are on the server)

- building a Discord community (only few joins)

- for another game in the past I've tried to put a popup message that mentioned specific hours for playing in the hopes that people would try to be online at these hours (it had no effect)

- posting on various reddits and indiedb/moddb, that worked but only rarely there would be multiple people online

Things I've dismissed:

- posting on Facebook and other similar sites, I don't have any experience with these and not sure it would be effective

- paid advertisment, I don't have a budget for it and don't think a general advertisment would work (it would need to be VERY specific to actually work - I've only witnessed it once in a specific Minecraft community where it was actually effective)

- posting on itch.io, it doesn't seem to have much to offer for propagation of your game and there are too many games already making it even harder

The game I'm trying to bootstrap is CellSplit, a survival 2D arcade game (an open source clone of Agario): https://www.cellsplit.org/

I've created it to solve the problem with teamers and griefers that plague the original game.

However my question is also a general one, how one can build a player base for their multiplayer game? Anything else to try?