Ushimaru is related to Zoro tho so he is a samurai
Yes.
The swordsman, who's fighting style and looks are the "spitting image" of Shimotsuki Ushimaru and who was born in the Shimotsuki village in the East Blue and trained in the Shimotsuki Dojo which were both confirmed to be started by a Wano native by the name of Shimotsuki Kozaburo belonging to the Shimotsuki clan, one of the feudal daimyos of Wano, has more stake for that claim.
Bonus:
The swordsman, who's fighting style and looks are the "spitting image" of Shimotsuki Ushimaru and who was born in the Shimotsuki village in the East Blue and trained in the Shimotsuki Dojo which were both confirmed to be started by a Wano native by the name of Shimotsuki Kozaburo belonging to the Shimotsuki clan, one of the feudal daimyos of Wano, has more stake for that claim.
Bonus:
I just showed that if we stick to the official meaning of Samurai the one I posted nor Zoro and Luffy can be Samurais but as most characters don't care about it nothing prevents Luffy to be called the monster Samurai
Luffy also share a lot of parralels with Oden so nothing is impossible
@ConquistadoR @L55