There are many opportunities to get arrested in Baldur's Gate 3, but the earliest and most "peaceful" opportunity happens in the Emerald Grove located in Act 1.
There are two children NPCs running a pickpocketing scam. Behind them, down the ladder, there is a hole your character can detect with a perception check. Enter the hole by either a) being a small race, b) being a druid and shapeshifting into a small creature, or c) using Gaseous Form.
Once inside, the "leader" of the children will have a short conversation with you and tell you you're not supposed to be there. If you refuse to leave, she'll begin counting to 10. Let her count down, without leaving, at which point she'll run to a guard and say you've been threatening the children. Let yourself be put in prison.
Once in prison, you can escape by performing an unarmed strike on the weakened wall. Jump from cliff face to cliff face, avoiding/disarming/destroying the explosive traps, and climb up the furthest cliff face. You should earn the achievement at this point, and you can return to your party by jumping towards the metal cage.