Filing 83(b) - 30-day rule

I was consulting a startup, received some restricted shares at a nominal value ($38 in cost basis, paid that amount). Grant date was 5/2/24, but only finished reviewing the documents, signed everything and accepted shares on 5/21. I assume it is still not too late to mail in 83(b)? Most sources say it is 30 days from *receiving* stock. Word 'receiving' is a bit confusing in this context.

Also, paper mailing 83(b) to IRS seems to be the only option, no way to do it electronically?

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