2021.06.18 17:25 "Re: [Tiff] IJG libjpeg-9d breaks libtiff JPEG-in-TIFF compression", by Even Rouault
Dropping Guido from the conversation, as I don't expect much sympathy from him to this proposal.
But I also agree that IJG versions > 6 are a dead end (Tom Lane itself acknowledged that long time ago in https://lists.fedoraproject.org/pipermail/devel/2013-January/176400.html). Unfortunately some distributions are still proposing them, at least Homebrew and Conda Forge (although they seriously consider migrating to libjpeg-turbo). What we can do is to socialize around in our communities to discourage their use, and at some point, we could possibly make libtiff error out at build time when encountering them.
My software is free, but my time generally not.