Publish Book to Blurb

The paper profiles (even if you could use them in LR) is useless. It is a single generic profile that we are supposed to accept and could be used for all papers and differing presses etc. The Blurb ICC profile is definitely GRACoL2006 Coated1, right down to the paper white L*a*b*. What they're using is essentially a copy of the IDEAlliance GRACoL profile and has little to do with how they're actually printing.

I have measured all the papers Blurb provides, and just the papers alone are not even close to GRACol 2006. In fact, the deltaE differences in just the two most different papers are nearly dE4!

Layflat:  'Standard Layflat' is also the only option I see. Have not tried, but, perhaps export to PDF, send the PDF to Blurb, and choose the Layflat paper options at the Blurb site.

Profiles: (In my simple understanding!) It is useless seeking Blurb Paper Profiles. LrC sends sRGB files to Blurb who then render your images for the printer they might be using. You would need to know which printer your book would be printed on to use a printer profile. In the past a CMYK profile was supplied for use with LrC, but it didn't last long.