Spark Mail (ignore the "AI Email" thing in the store listing, it's not intrusive or even a major part of the features) is a nice app and works with multiple providers. It even syncs which accounts you have added across devices.
It's... okay. I've been using it a lot, and at first it was claiming to be the spiritual successor to Google Inbox. I feel that, but it's also not that. I can't put my finger on it but it feels like it's evolving too fast and I just want its features to settle down so I know what I'm getting.