I've got around the 2fA/non US phone number by using a physicalUSB security key. BoA swear blind that there will be no problem, but I plan to visit UK before I move for good and try it out. SDFCU don't offer a physical 2FA option, but will send the code to email and they do use authenticator software.
I tried last week registering a USB security key (a YubiKey, in my case) with BoA from the UK as a means of 2FA, but without success so far. On logging-in to my account online (and having to phone BoA for an authroisation code just to login), the process of trying to register a USB security key called for me to enter (again) an authorisation code from BoA, and the BoA person on the phone seemed confused herself and wasn't able to help me with that step. But she
did say that such that 2FA via USB security key could only be used for authorising wire transfers, and not for logging-in to the BoA website. I.e. I'd still need a US phone number for 2FA to login.
It's not clear to me if the BoA person actually knew what they were talking about. Using a USB security key for 2FA is far from becoming mainstream, and BoA's people may or may not be fully abreast of what can and can't be done with one, or from what country.
As a short term means of 2FA, I'm temporarily paying for a US phone number from Talkatone. I've successfully registered that number with BoA, but the BoA person has told me that it can take a few weeks for numbers to become used by their system. Assuming the phone number does start working for 2FA, I'll retry registering my USB security key.