Embedded is almost entirely C/C++ - or assembly if you're hardcore.
But there are a few exceptions (neither of which run on Arduino boards)
There is a javascript interpreter that runs on some higher end microcontrollers Espruino - the Espruino Pico and Espruino Wifi are nice development boards - though the performance of the JS interpreter isn't so great.
And there's NodeMCU, the Lua interpreter for the ESP8266, if you're some kind of freak who likes lua.