My suggestion is to make the house unshowable in ways that aren't illegal to do so. Porn/nudity is an extreme no no as someone might bring a minor along for the house showing. You can legal/technical that advice all day members of reddit but being a sex offender isn't a technicality as much as it's a technicality.

Stick a dildo on the inside of the front door. Get some anal beads and hang them from a wall with a giant poster that says worship above them. Shit on the floor. Shit in the shower. Put shit on the anal beads. (or chocolate fudge) Leave the toilet open and filled with shit and piss.

Hardcore yell I'm masturbating when you're locked in the bathroom and flip out about how you never get privacy. Walk around in your underwear, with shit stains on them. Lay in the middle of the floor during the showing and don't do anything. Yell and scream loudly every time there is a showing. Play extremely bad music and refuse to turn it off or down.

Stick that he man hey yeah video on repeat in the front room. Invite a ridiculously large amount of people over for a party during the showing time. Invite them over for a movie and have all lights in the house off, yell and complain very loudly if any light is turned on. Watch the he man hey yeah clip with them and act like it's utterly interesting.

Let them know not to go in the bathroom, don't explain why, mention that you shit in the shower if pressed. Walk into a roommates room and ask them why they shit in the shower again.

Get a bunch of paper cups, place them around the house in inconvenient places and explain it's for a school project. Flip out when they are knocked over. Cry.