Good news, I’ve fixed it!
Today I’ve downloaded Vivaldi browser just to test it out, and noticed that it had the same exact issues - this meant that the cause wasn’t probably in the browser itself. So I got an idea to reset “Global settings” to default in NVIDIA Control Panel, and IT WORKED!
SOLUTION: Reset “Global settings” to default in NVIDIA Control Panel.
This means that it was caused by some setting in NVIDIA Control Panel, but I can’t tell which one.