https://bugzilla.redhat.com/show_bug.cgi?id=1779123
--- Comment #4 from Nicolas Mailhot nicolas.mailhot@laposte.net --- As for conversion to OpenType, CFF OpenType (OTF) was specifically designed to allow Adobe converting its large store of Type1 fonts to OpenType without data loss (the outline format within OTF is pretty much the same as within Type 1 fonts).
So Type 1 conversion is mostly opening up Type 1 font files in fontforge, fix the font metadata (all the metadata available or strictly specified in OpenType, that were missing or badly specified in Type 1, and saving the result as OTF.
Since a lot of real-world fonts have garbage in their metadata fields all that matters practically is fixing the naming fields ie apply OpenType Name ID 16/17 rules instead of reporting the limitations of Type1 naming in OpenType https://docs.microsoft.com/en-us/typography/opentype/spec/name#name-ids
TEX Gyre took a lot more work than that because the project was not just converting legacy Type1 fonts, it was fixing and extending them.