Types of Subplots for a Story
a person with authority over the MC being very flawed: incompetent, malicious, untrustworthy, ...
inner struggles of the MC: self-doubt, overcoming trauma, proving self to others, ...
romance: love triangle, a fracturing established relationship, pursuing a crush, ...
trying to preserve a key element of MC's life: town, job, family business, house, relationships ...
trying to uncover or keep a secret
And remember, any subplot you chose should service the main plot either directly or indirectly, so adjust as needed!
