During a recent fall, my chain came off my front chainring, and scratched up my frame. It looks to me like it's just the paint that's damaged but would appreciate a second opinion. The bike is a Trek Domane SL5 2021.
The following pictures are unfortunately the best I could do w/o taking apart the bike.
It's very likely only cosmetic, but the fine hairline-looking scratches (hopefully only scratches) are not the most common thing to see in damage that occurs from a dropped chain.
The other thing to be aware of here is that most of the time, damage from chain drop affects the chainstays and bottom bracket. Here you've got it up into the down tube. That area is going to be much thinner-walled than a chainstay. It's reasonable to be cautious in this case, particularly if the chain not only rubbed that area but also got forcibly stuck and ground against it.
What you should definitely do is pull the cranks off and do a "tap" test. Starting up higher on the down tube, tap it gently with something like a plastic tire lever and observe the sound. Keep tapping down until you get to the damaged area. What you're looking for is a sudden duller, less resonant sound in that area. This test is good at not providing false positives; if it does get dull and less resonant sounding right in that spot, yes you probably have something to worry about.
What I would also do personally, even in the hopeful case that there's no sound change and you decide to not worry about it, is use a very fine grit sandpaper and smooth out the scrapes in the painted surface until you can see that it was just in the paint. Then I would put a thin frame protection sticker over the whole area, rationale being that over the life of the bike, there are decent odds this won't be the last time.
Finally, the bike appears to have a chain catcher. Make sure it's adjusted right, i.e. as close to the chain as possible without rubbing. Usually they should be able to prevent what happened here.
