How about Aslan Karatsev?
I think he already made a breakout run this year, reaching as high as SF in Australian Open, beating Schwartzman, Félix Auger-Aliassime and Dimitrov.
Winning doubles with Rublev in Qatar Open. And then the singles in Dubai last month, beating Sonego, Rublev himself and then Sinner.
Won against Djokovic in his hometown in Serbia this month, but lost to Berettini in the finals. So I would say that he has also a bright future, although not that young at 27 years old, but he is peaking at the right now and can content in future grand slams.
27 years old is kinda late for him, i wonder why he didn't show up till now, i have never heard of him before untill this year, maybe it's not too late for him but the competition is really hard right now with Medvedev, Tsitsipas, Thiem and of course Nadal and Djokovic and maybe Federer, it won't be easy for him to win a big title, and to be honest i don't think he can.
I agree, his kinda late on the fun, although he can still compete at high levels and give everyone a run for their money. He already beat the number one seed, so he still has what we can call a giant killer. And he can put a big test on the young players, specially Tsitsipas and Thiem as he seems to be a clay court specialist to me. And he could pull some upsets from time to time.