Can't open .jar files

You can have multiple versions of java all installed at the same time.

You call java from the particular version folder inside /Library/Java/JavaVirtualMachines/

Your path is calling the Java 8 version. Your PATH is not updated by installing another version of Java.

Copy/paste this into Terminal and run it:

/usr/libexec/java_home

That will list all installed versions of Java.

The java executable is in the Home/bin/ folder.

Oracle Java 14 seems to be the current Oracle software for macOS.

https://www.oracle.com/java/technologies/javase/products-doc-jdk14certconfig.html

Here's the install and setup for Java 10—there's probably a newer download...

https://docs.oracle.com/javase/10/install/installation-jdk-and-jre-macos.htm

This looks to be newer:

https://jdk.java.net/14/

Try a reboot? I'd guess that the issue here is that the Java root has not been set up. A reboot and logging in anew might cause that all to start working.

Failing that, then Contact the Minecraft folks, and maybe then the Oracle folks, as they support Minecraft and Java.

Related:

https://help.minecraft.net/hc/en-us/articles/360035131371-Minecraft-Java-Edition-system-requirements-

Oracle indicates they're having issue passing the Catalina app security checks:

https://www.java.com/en/download/help/catalina_java.xml

https://www.oracle.com/technetwork/java/javase/using-jdk-jre-macos-catalina-5781620.html

Entirely as a side matter, check the licensing for Oracle Java, as there's a commercially-licensed Java option installed with recent versions of Java. This commercially-licensed feature was enabled by default when last I checked, too.

Piles of error codes and ginormous stackdumps, well, yes, that's pretty much what unhappy Java does.