Tail lights/rear brake lights, seals.
tail/break light wire harness/cables seals (that go thru the sheet metal to the plug/back of tail/brake light housings & light bulbs) check those.
The trunk weather strip seal, replace if needed.
Body panels not sealed or the body panels sealant has become brittle, loose, or just failed from time, wear & tear, body flexing has allowed water to trickle in.
All vehicles are made to have holes of various sizes like swiss cheese to allow & accommodate the various miles of wires to parts & components, all cars have these. May want to on a day off take out & remove the floor pan carpet, seats, trunk liners & look for open uncovered holes & close with rubber tops/covers or flex seal tape. You can use different sized items from around the house to draw the circles on flex seal tape or use sockets.
The rocker panels, the floor pan, trunk area, underneath the rear seats are bad & have open exposed holes that you can see to the ground. You can use a wire hanger, weed eater/whacker line or flashlight to find s many holes you can cover.
That's what I've done & still doing. Just looking around & covering them up with flex seal tape on both sides.
If you have a sun/moon roof, replace the window assembly weather strip.
Check the antenna rubber seal. If you go thru Automatic car washes every time, the brushes yan, pull & tug with force on plastic weak trim parts that it eventually will break & cause leaks. For that you need to remove the headliner. If there's water spot/wet spot where the antenna is, there's a leak.