Is it normal?
We can't know whether it is normal for that board, without seeing (and then analysing) its true schematic. (I specifically say its true schematic, as I've occasionally seen schematics provided for boards by vendors, after many requests, which didn't match the actual board!)
Unfortunately you have now seen the trap of these pre-built cheap boards, which are usually supplied without data, schematic, or even much confidence that the main components or specifications are genuine :-(
That op-amp being hot might be typical for that specific board, due to a valid design decision. Or it might be that the device marked LM358 is really a copy of the original device, which responds badly to that specific design and will have limited life, although an original LM358 would be fine. Or any of several other possible reasons...
Without having the schematic, some confidence in the origins of the components, and then perhaps needing to perform further measurements e.g. with an oscilloscope, we can't know the expected behaviour for that board. As I said, that's the trap with such boards - lots of unknowns...
You could start by buying another one of the boards, taking photos of the locations of the components, and then desolder every component until you are left with a bare PCB. Then reverse-engineer the schematic from the tracks on the bare PCB and the devices which you removed (you might need to measure unmarked components e.g. some L & C, using a suitable meter). Then you can start to evaluate why that op-amp is hot. As you can see, this isn't something which we can do for you "remotely". :-(
I see your options as including either:
- get the true schematic from the vendor; or
- reverse-engineer the schematic yourself; or
- trust that the designer knew what they were doing; or
- accept that you'll never know whether the board is truly working as designed.