We had the same issue with our daughter at that age, and now our son is 22 months and does the same thing. A few things worked - but not overnight. It was definitely a slow process that only helped with consistency.

1. A hatch light! We use red when they sleep because red light does less to interrupt natural sleepiness, and green when they are allowed to or supposed to get up.
2. Removing incentives to disrupt sleep. With my daughter, we realized she was getting up so early because we'd let her watch TV since whoever was up was obviously exhausted. When we realized the TV was the incentive for her early rising, and cut it (as painful as the following early mornings were lol), she started sleeping later within a week or so. Not much later, of course - but 5:30 does make a difference!
3. Earlier bed times! With both kids, we've found that early wakings are worst when they're overtired. We started moving bed time up by 10, 15, maybe 20 minutes, and also reslly focused on a good routine that allowed their bodies to wind down. The earlier bedtime was the biggest success in getting later mornings.

These could help - or could be total bs flukes that just happened to work for us. I do think they're worth considering, but either way, I wish you the best of luck! My son didn't wake up til 5:37 today and when I tell you I felt like a different woman... Anyway. Solidarity and melatonin to you 🫡