My solution is to run with as few as 2+me (the DM), and use a play structure that doesn't require the same players to be present at every session. We always end rhe session in a safe location (town, safehouse, etc). If someone can't make it, they're just in suspended animation along with their gear and hirelings/retainers until they're back.

Just not sweating the fact that it's a game has gotten me a very consistent game every two weeks like clockwork.