Back in the day when Ford still made the Crown Vic we would bypass the door plunger switch for that very reason. The dinging would give away your position if you were trying to be quiet (law enforcement).....I think there is a rubber booted button/switch on the door jam of the Crosstrek??
We also bypassed the ignition steering wheel lock with a toggle so the key could be removed while the car was running and the wheel could be locked or unlocked with a hidden toggle. Cool feature to keep the car running and nobody could steal it.
You could just make a semi-permanent alteration to the door switch. It’s the black thing near the door striker. Remove it and assuming it’s a normally open switch, because it sounds the most logical, pull the connector, attach it to something so you can retrieve it later, shove it back in the hole and put the switch back.
If it’s a normally closed switch, just unplugging it will work.