Forge 1.14 port does not work

[unascribed]

I'm unable to get a Forge 1.14 or 1.15 dev environment to work; the error is always a variant of Could not find net.minecraftforge:forge:1.14.4-28.1.92_mapped_stable_58-1.14.4. - I've tried many mappings versions and different Forge builds, latest and recommended, some just random, and it simply doesn't work. It seems like the needed files were just deleted from the Forge maven.

I don't dare try and ask questions in an official Forge channel, as I will certainly be immediately banned for the cardinal sins of working on 1.7 mods when 1.7 was still relevant and for alluding to the fact I was using ASM while asking a question to avoid needing ASM in 1.8.

Hoping someone who knows how to fix this will stumble upon this issue.