Please refrain from using “head gasket sealants”: these are mostly intended to seal coolant leaks and they will most likely make more damage than good as they tend to contaminate entire cooling system. besides, you do not have a COOLANT leak.
The picture you submitted covers too little area to get a good idea where the leak is located.
Look at this picture, this is the same EJ253 you have, but it’s a remanufactured engine with valve covers removed:
I marked location of head gaskets as red and valve covers/gaskets (removed on this picture) with green.
It will be next to trivial to fix valve cover leaks. If you go for gaskets replacement, make sure to replace spark well tubes seals too.
If you have headgasket leaks, do not use “sealer”, you will regret it later. Go for proper fix.
@ok4450 suggested before he was working on a number of Subarus in dealership shop and I believe he ws suggesting tightening head bolts. Hopefully he would chime in with some better advise.