Firstly, can you ensure that your room bulb does not use low PWM? If you have a phone that is able to record in slow motion, use it. It could be possible that when you place your monitor in front of a window, the flickering is less obvious.
Next, is your wall painting white in color? I just did an experiment by staring at my white painted wall while being a meter away. It was the area that was refracted by my bulb. It felt extremely uncomfortable. It never occurred to me since I would always I always look slightly downwards towards the table.
I can't comment on the above ASUS monitor, but I suggest you adjust your monitor to be somewhat similar to the picture below.
source: https://ergobuyer.com/blog/eye-strain-neck-pain-and-monitor-ergonomics-conventional-wisdom-vs-ergonomics-evidence/
What this means is to elevate the tip of your monitor screen to be below your eye level.Additionally, it also means that your eyes will always be looking slightly downwards. When you do so, your eyes are more relaxed. Below is another picture.
Source: I major in ergonomics 🙂
In my own personal experience, the optimal elevation of the monitor is where the top of the monitor screen is somewhere directly below your nose.