I think the Spacecraft Interfaces section (starting page 84) is the bit that might interest HN readers. It describes (to potential customers) the dimensions of the payload bay, electrical and comms interfaces available, conditions the payload must be able to tolerate (vibration, temperature etc).
The issue is that Europe does not have the market for a reusable rocket and though there are a few initiatives for creating one, the current policy is for maintaining launch capability for only a few satellites yearly. If the EU decides to make One Web truly massive, things might change.
Just FYI. Almost every launcher that offers commercial services has such a user manual. I was involved in preparing one such manual. A collection of these manuals can be quite entertaining for 5 year olds. You should be able to easily find them from the websites of the respective companies or agencies.
https://ntrs.nasa.gov/search?q=shuttle&page=%7B%22from%22:0,...