Back to Disco Elysium
At this point Frittte will be open again. You can shop one last time for any medicine that you may need. You should have enough points and medicine to cover five or six points of damage to both Health and Morale before continuing.
Make your way back to the fishing village and speak to Lilienne. You can find her by the docks. Ask to borrow her boat and she’ll let you sail it across the sea. Once you’re on the boat you’re committed to a linear path to the end. There’s no going back to complete any quests from here on out.
Once the boat arrives at the island climb up the hill and enter the building. If you sleep in the bed it will trigger a long optional sequence.
Climb down to the lower floor and walk southeast under the catwalk. head through the door to the outside and climb the small hill to the other small building. Grab the LUM Fuel Canister and return to the larger building. Use the fuel on the generator and then use the control panel in the southeast to open the blast door.
Head through the blast door and talk to the person by the fire. Make your way back to the boat and sail it back to the fishing village. After one final conversation the game will be complete. Congratulations on completing Disco Elysium!