I've have spare set of Osram aftermarket led daytime running lights.
They are straightforward to install so no problem with that.

What I am interested is that how I can turn off built-in low beam Drls?

My Rx has the setup that when the lightswitch is in off-mode or in the auto-mode daytime, my lowbeams, front parking lights and rear lights are on.
So technically they are not Drls but lights are just on all the time.

 

In the USA it is just a matter of switching a 5-pin relay with a 4-pin relay but I am sure yours would be wired differently.

 

Thanks, yes I've read those threads. I could start to examine that relay if it exists in my car. Based on other Lexus/Toyota model local discussion, procedure to turn lowbeam drl off could be something more complicated.
Before the time of real Drls we had here just rule that driving lights had to be on all the time. That's why my Rx has time setup.

 

You might want to ask the dealership. I know that here in the USA my BMW dealership could turn them on and off for me and I think the same is true of Lexus. Don't know if they can over there but it doesn't hurt to ask.