How many miles do you have on it? Oil usage?. Our '17 used no oil with the 0w20 but its was vary clanky when hot. Like "I wouldn't buy that car, the engine is shot" clanky. Our new 2023 was dead quiet then it started knocking after about 3000 miles in service. It uses about a quart over the 6k mi. OCI. I don't know what's up with these boxer engines, the last well running one was the great 2.2 in a 1996 Impreza wagon.
I wouldn't go near a 16. I top off with 10W30 and the engine is much quieter with a bit of that in there.
But the 2.0 FB don't like 5W30 - they wont run well. Sluggish.
Genuine Subaru 0W20 made by Idemitsu in Indiana is a good oil. It runs clean, the engine makes good power on it and is very responsive. Better than any other major brand - save maybe the old M1 EP 0w20. The new formula is no longer a majority group IV - a true synthetic.
Stay the course.