Currently, lldb only supports debugging riscv64 programs locally, due to the unfinished ABI support (which is necessary for remote-gdb debugging).
For your problems, we lack information about the version of your compiler, your program source code, and your command line to compile the program and launch the emulator and the debugger. I can confirm gdb is able to debug llvm compiled executables, which is used in differentiation testing. It is hard to say what is wrong with only this error message.
I find this patch helpful if you are interested: ⚙ D62732 [RISCV] Add SystemV ABI