When I got my IRS online account a couple years ago, the verification method involved cell phones. But because the IRS could not find my cell phone number in whatever government database they were using, they mailed a code to the address on my tax return, and I was able to enter the code and complete the registration once the letter arrived.
Unfortunately, it seems that the IRS has changed their verification procedures for establishing new online accounts, and since I already have an account, I can’t try to sign up again to test the new verification procedure.
You may be able to go to a local IRS office to verify your identity, but I don’t know if they have open office hours yet and they are backlogged with everything due to Covid.
