Is a Sub required for HT

Yes.

No....but!

Your receiver's bass management will route all the bass to existing speakers.  The experience of watching a movie with a well i tegrated sub is transformative.  Especially naval movies, but integrating a sub well is a ton of work to do rignt.  if you cant take that effort, leave it out.

To do subs well usually requires bass traps and DSP in that order.

I already have GIK room treatment, including bass traps. I don't understand why you say integration for HT is difficult? I won't be using a sub in my 2-channel system.

I don't understand why you say integration for HT is difficult? I won't be using a sub in my 2-channel system.

It's really not hard to add a sub to home theater.  2 channel yes, but HT is a walk in the park.

I agree that the sub will make a movie that has that LFE channel a whole different experience.