I'm still missing this profilles. I imported several files from both my A7R4 and A74, no preset applied. For the A7R4 the camera profiles are available, for the A74 they are missing. Firts I assumed they wern't available waiting for an updat of Lightroom, but no..
If you're not seeing the camera-matching profiles available in the Profile Browser, then:
1. Do Help > System Info and make sure you have the latest version of LR installed (11.5). If not, do Help > Updates.
2. Make sure you are editing raws and not JPEGs or other non-raws -- type "i" in Develop to ensure the file name ends with .ARW (see the screenshots). Many users have posted here thinking they were editing raws when in fact their camera settings had gotten reset and they were editing JPEGs.