The air conditioner filter of the new Suzuki Jimny (4th generation, from 2018) is located behind the glove compartment.
To replace the air filter, do the following:
1) Remove the glove box.
To do so, release the mounts by pressing the glove box on both sides and pulling it down.
2) Remove the cover by pressing the fasteners and pull out the air filter.
Insert a new filter by making sure that the «UP» mark points upwards.
Lift the glove box and close it.