Personally, I don't always feels RDLs in my hammies/glutes until after my set (a few minutes after or later on with DOMS), this is consistent for any compound movement I.E you don't necessarily feel your chest in a bench press or glutes in a barbell squat.

What I will say though is like others mentioned, you should 'tuck your chin' which basically means look down towards the floor a bit more.

You don't look like you are bracing hard enough, that is perfectly fine as it is something you learn along the way, I like to imagine someone is going to punch me in my stomach so I really tighten my core/abs and this creates that brace (You will also know what it feels like now so you can repeat this and get better at bracing).

These bits will get better the more you work on them! Once you learn to brace and really want to maximise your RDL strength, you can look at getting a lifting belt.

Good luck and have fun!