Will unincorporated distros who don't comply be illegal to use in the areas passing these laws? This isn't "obscenity" -- isn't there a first amendment argument for these projects?

There is a strong 1A argument, and one such law has already been defeated: https://netchoice.org/netchoice-wins-permanent-block-of-loui...

Bernstein v. United States set a precedent that has not yet been overturned.