I imagine no matter how it's done, it will involve some amount of manual approval. I would be pleasantly surprised to learn that this can be automated.
Credit card, SSN/tax ID, scans of Passport/ID card - some of this is done by online-only financial services (eg Petalcard)
There's also tools like DocuSign, multifactor authentication mechanisms (SMS + TOTP app + email, etc)
If the service/tool is only "supposed" to verify certain types of accounts, you might require the use of specific format email addresses, too (has to end .gov, .edu, nytimes.comm etc) - this can lend itself to organizational verification (gonna be harder to spoof (and therefore easier to verify) harvard.edu than blurblebuck.me)