UNET deprecated. now what for solo poor developers?

Hello, I am a solo freelancer that wants to make a multiplayer games that also will help charities community. I can't afford to pay for these since the game is freemium an I have no guarantee of paying players.

IF i want to use the unity multiplayer system do I need to pay for the personal or pro licence? Can i make a free multiplayer in case I don't earn almost anything? I knew that if I have a certain revenue I need to pay Unity license (over 100000eur) and that's totally fine for me because I can earn. But I want to know if is possible to make a free multiplayer game if i have no revenues?

Also, I read UNET is being deprecated. But then what can i do to make a multiplayer game? do you have a tutorial to build the game with the new system for free? thanks !

my game is a 4 players arcade game where each player updates its score and send an attack. the ideal update rate would be 3 seconds (shorter is better) but since i cant afford much, i might accept a 6/7 seconds delay!

Also what do you guys do when you have 100000 players playing with your game and none of them becomes a payer? how do you sustain these costs? What are your solutions?

Thanks