Is there a simple online testing server (similar to Postman-echo.com) that I can use for JSON-RPC commands from Postman or for any other simple scripts that I might be writing?
On GitHub, I see lots of public APIs on GitHub (many that don't even need keys), but I unfortunately don't see any for JSON-RCP that I could use.
I also stumbled across this Guru JSON app, but it seems to only let me send JSON from the website, not from other apps like Postman.
I found Random.org and just tested it in Postman.
https://api.random.org/json-rpc/1/invoke
Works great for learning purposes!