Can /e/ OS be used with republic wireless and Samsung s9?
No. Only the Factory Android OS is supported.
Republic does not support Custom ROMs.
You can not use a phone with a custom OS on it and have it work on Republic.
This is partially because the RW app and they way the proprietary and patented tech that RW uses certain APIs and things that have to be in the Android OS that most likely would have been stripped out or modified in a custom OS rom.
Anyway… Android is made by google. You buy a Android phone, you are buying Google.
The phone is meant to work with Google, trying to avoid that, it cripples the phone more so that if u were to use a dumb flip phone. If you want privacy, then I hate to tell you, you wont find it in a smartphone.