What is the alternative if employee is not living in the rental space for HRA (house rental allowance)

You could pay rent to even your parents if the property is in their name. But have to be mindful of the fact that your rent will be their income.

But with flexi salary Strcturing we can change the format right?

Need more context. Firstly, I don't think changing the salary structure at this point of FY would be something any company would allow.

Rightly said @Anshul Sharma. We shall also be doing this while working on the appraisals.

I was talking about flexi pay or flexi benefit employees can change HRA to LTA or mobile food expenses to save taxes if they are showing bills.

Yes, they can. For that, it's necessary that they had opted for that benefit at the start of the FY while giving declaration. If it was opted, then yes the amount can be changed subject to proofs.

Yes I know it, I was looking for alternatives and I found them on research thanks