The issue is it errors on use of the "Test Connection" button in "Configure System". It tries to load "org/bouncycastle/asn1/DERObject" for the "EC2 Key Pair's Private Key".

Fedora includes BouncyCastle 1.50, which drops the org.bouncycastle.openssl classes required by ec2-plugin 1.27. ec2-plugins includes the older version of BouncyCastle, 1.40, but the system version overrides it.

So I set maven to include plugin libraries and classes in the Classpath version during compile. Along with explicitly masking org.bouncycastle. I created a pull request on the ec2-plugin github repo, PR #145. An alternative fix would be to rewrite the ec2-plugin to use the newer version of BouncyCastle, or rewrite that part to use a library other than BouncyCastle.