How Many Players Does BOMBANANA! Need? Exactly Three

Three. Not two, not four.
Both official sources say the same thing. The Steam store page lists "3-Player Co-op — No more, no less. Exactly three monkeys required." The official FAQ answers the question "How many players do you need to play?" with "3 players are needed!"
Why it is fixed
The design does not scale. There are three handicaps — blind, deaf, mute — and each one holds a piece of information the other two need. Remove a player and a piece of the bomb becomes unreadable. Add one and there is nothing for them to do.
Can you play with two players?
Not through any official mode. This is one of the most searched questions about the game in several languages, and the answer is the same in all of them: the game requires three.
Can you play solo?
There is no official solo mode. You will find videos titled "how to play solo in Bombanana" — those describe workarounds players have found, not a supported feature. We are not going to document them as if they were official.
Are there bots?
To be confirmed. Players ask about bots to fill an empty seat and we have not found an official answer either way. Nothing in the store page, launch notes or FAQ mentions them.
If you are short a player
The Global Lobby Browser exists precisely for this — browse public lobbies and join strangers. The official Discord also has find-a-team and lfg channels where people post room codes constantly, in several languages.