Hi! Haven't had the chance to run it yet but from reading it, here's what I can give as answers :
- Hungry Gnolls Eat The Rich doesn't recommend a specific number of players, so you can assume that like many ttrpgs it's best suited for one GM and three to four players.
- It doesn't recommend a specific play time either, but it's not a one-shot system and can be played as a short form campaign.
- There is no solo mode.
The games is as rule-light as they come, so it's pretty flexible when it comes to number of players and playtime.