digi tacho card

Rav:
If you hold a GB photocard driving licence you can (should?) use the form you found, i.e. the d777b/dl:

You need to use form D777B/DL to apply for a for a digital tachograph driver card if you hold a GB photocard driving licence. A new photo is not needed

Cheers
Rav

You won’t get a from a post office, only download or sent through the mail from DVLA.
Rav nailed it, good link.
There is a paragraph on that page that says…
This form can only be used by existing GB tacho card holders and EU/EEA or Northern Ireland drivers who hold a tachograph record at DVLA. If you do not hold a record or are applying for a renewal you must use form D777B available from Download and order DVLA forms - GOV.UK.
Not true. This is the form that you use to get your first card, not just for existing card holders.