Do you mean the stock AOSP keyboard? How to you ratchet down permissions on it?

Reply to this note

Please Login to reply.

Discussion

Long tap on the app icon. Go to App info. Remove Network permission.

Still tryna figure out what "mainstream keyboard" is

Probably the stock Android keyboard - GBoard?

Doesn't come asking for network permissions out of the box on GrapheneOS.

Sorry I was gone. Yes mainstream like SwiftKey or Gboard