I live with roommates and came home from vacation and realized someone had been in my room. What are some good locks I can get for a bedroom?

I rent so I can't do anything too much. I know someone was in my room because I use Alexa to turn on and off my lights and the light switches had been messed with. It does not seem like anything was stolen thankfully! I feel a little uneasy knowing someone was in my space. Any locks that are good for that... show more I rent so I can't do anything too much. I know someone was in my room because I use Alexa to turn on and off my lights and the light switches had been messed with. It does not seem like anything was stolen thankfully! I feel a little uneasy knowing someone was in my space. Any locks that are good for that situation? My roommate has a new boyfriend who seems very sketchy so I am thinking it was him (I haved lived with my roommates for years without any issues like this before!)
Update: It also could have been my landlord, he is known to come in unannounced and has been harassing me. The chances of him letting me change the doorknob is low.
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