Sure there is: tools like strace, dtrace and eBPF let you “peak under the hood” of nearly any application, not to mention disassemblers like IDA Pro and Ghidra.

Sure there is: tools like strace, dtrace and eBPF let you “peak under the hood” of nearly any application, not to mention disassemblers like IDA Pro and Ghidra. I have debugged all sorts of issues with closed source applications using these tools.