

Your Android device doesn’t have a personal dictionary section in the Language & Input page? What phone do you have? Yeah, keeping it offline is probably fine, but I’m just surprised since this has been a thing for at least 7 Android versions now, as far as I know.
By the way, HeliBoard (an offline fork of the now-defunct OpenBoard) seems to have its own private, built-in personal dictionary; I migrated to that since finding out.
US Mobile is a self-proclaimed “supercarrier” which offers SIMs across all major networks (AT&T, Verizon, T-Mobile), so you can change as you like according to your phone’s compatibility. However, the CEO (who is active on /r/usmobile) has been known to kick existing customer loyalty to the curb in favor of new members, and their customer service centers are in Pakistan, where he’s from.
These may or may not be good or bad things depending on your threat model, but one thing’s for sure: their price is unbeatable! Come to think of it, I have a referral link for anyone who may be interested, but that’s up to you. I actually dislike the CEO’s practices, but I’m already locked in for a year and didn’t know until later…