For me it has to be AmberELEC.
Video previews, the option to view a game guide, and an icon on the games list to indicate a game has Retro Achievements combined with an easy to view list of achievements.
It was fantastic and the reason I’m hesitant to sell my RG351V
Doesn’t OnionOS on the Miyoo Mini Plus support RetroAchievements?
Yeah, that is what I wanted to imply at the end of my comment but I had a typo.