You can now transfer crypto into ameritrade and those other wall street brokers? Is this something new?
No, you can you use them as your checking account to get fiat to Coinbase / Gemini
There is no worry about any issues with other checking account providers since although it looks / feels / acts like a checking account it's actually part of a brokerage account.
I know several people who have used them for checking while only keeping a minimal amount in the brokerage part.
That or you can just fix your issues with chexsystems. Call your state banking department if you can't get satisfaction:
https://www.csbs.org/state-bank-agency-contact-quick-access-Dave