You can do the manual scan directly, you don’t need to do the folder scan first.
I’m not understanding this, don’t they all show up for you in the manual scan?
If so, you are doing the scan wrong, you should get everything with the same extension you put in, because this scan skips the check.
RetroArch has a different scraper than other frontends, because it is based on checking that the image is correct, verifying the crc and sha codes.
That’s why it uses tested sets like No-Intro, Redump, Tosec. The game lists in RetroArch are created based on the official .dat files published by each project. Every time those projects are updated with new verified files, all the dats are converted to lists, but, this process is not instantaneous, sometimes it takes a long time.
About the friend lists, maybe they are already updated and that’s why you have them in the current RetroArch, for Lakka, you’ll have to wait for the next version to be released.
It would be wonderful to have a txt output with the missing games, but I don’t know if it can be done or if it will ever be done.
One clarification, “rom” is chip, it’s nintendo, genesis, etc. Gamecube is “disk image”. ISO is a type of disk image. Redump normally uses the cue+bin format, or converted to .chd