There is an interesting thread on the Forester board where the poster is considering changing the complete headlight with different year model. Its a great idea actually but I am curious if it will fit.
https://www.subaruforester.org/vbulletin/f85/2017-led-projector-headlights-2015-halogen-792023/
I have the same vehicle and I am going to replace the headlights soon, but this idea feels better, although way expensive than just replacing the bulbs.
Replacing headlight is a lot of work and they will need to be adjusted by a Subaru dealer because they could blind other drivers. Replacing bulbs is much more easier.
If OEM Numbers match then it’ll be no problem I think
If you choose this route, be sure to check if there are on there electrical modifications required. They might be plug and play, I don’t know.
Look up aftermarket units. If they cover both years in question, odds are very high they will work.