Hi,
i built a tool called cardano-signer a while ago, it is capable of signing hex, text and binary data with any key that is used in the cardano environment. it can also do verification. in addition it can generate CIP-0008 signed data and voting registration/deregistration inkl. voting-power delegation via CIP-0036 signed data too.
So if you need a tool on the CLI to sign/verify things, you can use it. Also useful as a debug tool for own development, etc.
Starting with v1.9.0, Cardano-Signer also supports the new deregistration metadata signing for CIP-0036.
Have fun with it, Martin