2.1.27 does have some CLI support, though it lacks many features added since then.
You don't need to use the CLI if you have .spine files. You can just open those with 4.1, or export them from the CLI with 4.1.
If you only have JSON files, that's a bigger problem. 🙁 2.1.27 doesn't support importing a JSON file into a Spine project from the CLI. You would need to do this manually: open 2.1.27, import a JSON file into a project, save the project as a .spine file. Once you have .spine files, the above applies: you can just open them with any newer version of Spine. Note you have to do this once per JSON file, not once per animation.
How many JSON files do you need to do this for?
Depending on your JSON files, you can try importing them with 4.1.
