itch.io  has many indie games

 cardgames.io  for solo Hearts and other card games

 boardgamearena.com  has many games including multiplayer

 happymeeple.com  is great for beginning gamers

 playdiplomacy.com  for online Diplomacy

 gamesgames.com  has assorted games

 kongregate.com  also has a wide assortment

 thegeneralshq.org  for real human hexmap wargames



 Google search  for "online free games"