All I want to do is play Minecraft.
Well, that's not true. All I want to do is play a specifically modded version of minecraft that requires (specifically) Java 8, while my friends are online, and a more vanilla version of minecraft that requires (specifically) Java 1.16 when they're not. There is no issue with me logging into remote servers with the Java version 1.16, but the Java 8 version constantly returns, "Mojang authentication servers are down", so I went down a rabbit hole and figured out that maybe this has to do with out-of-date ca-certificates in the Java 8 installation. Easy fix, right?
I installed Java 8 from the ppm, and Java 1.16 from a tarball, meaning I can find the 1.16 files in the file explorer, but not the Java 8 files, so I cannot simply copy the known-good certs into the older version's folder. I uninstalled the Java 8 certs using the ppm, and now it warns me not to install any certs because the 1.16 certs are already installed.
But the minecraft multiplayer launcher still can't contact the mojang ssl widget. How do I get Java 8 to "see" Java 1.16's ca-certificates?