As a savage Link main, there are only a small few matchups that are "bad" for Link. Literally just a few. Chrom isn't a "bad" matchup to be honest. I just think you need to get used to spacing and using angled boomerangs on him. The following Characters are the actual notable bad matchups for Link.
Megaman 80/20 = Just using his lemons is enough to turn off half of links tools.
Zelda 60/40 = Neutral Special and Phantom. Many links need to lab out how to get around that fact that Phantom is a lasting body that block projectiles, even after launching its hitbox.
Olimar 70/30 = It's obvious why.
Other than these matchups, there are no troubles if you aren't a spammer with projectiles. It's the spam style links that have trouble with people like Chrom or Lucina, or Sonic for example. I actually believe Sonics speed is a very big weakness in the Link matchup because it's harder for them to stop. Captain Falcon actually seems to be better in the Link matchup than Sonic does. Falcon has actual good kill options against him.
To be honest tho, the only matchup you should be concerned about is a GOOD Megaman player because all they have to do is A button to cancel your midrange game and then get you offstage for an almost free fist edgeguard. It's literally one of the worst matchups in the game.
Samus again, like it is the case for Chrom and other faster characters, is only good against bad online habits like mindlessly spamming projectiles. If you pull your bomb in the air while moving left in right instead of while standing still, and throw the boomerang while moving instead of while standing in place, Samus has little to no "get in" options. Yeah she has charge shot, but you have a shield that is so good that you can just stand there and that charge shot will do nothing. Her missiles are easy to avoid because they are slower than Link is and you can shoot it with the tap of the B button (arrow) or do a fade back bomb drop.
As I said tho, after putting almost a thousand hours into Link, this is my knowledge of what is and what isn't good against link.
EDIT: I forgot to mention that Wolf is also a bad matchup, but that's true for most the cast because Wolf is literally one of the more unbalanced characters in the game and to be honest, 95 out of 100 Wolf mains are carried by the Character. To beat this matchup, it's easier said than done against a REAL Wolf main. But against one of those 95 carried Wolf mains, just bait out reflector. Super EZ.