Dear @ajit ,
First of all, I would try to install ROOT via your system package manager or, failing that, via conda (you could even use mamba for faster installation, as I suggested in other posts).
If you are still sure you want to compile ROOT yourself afterwards, just build without -Dpyroot_legacy=ON and see if that is enough. Remember that you still need to source thisroot.sh after compilation if you want to import ROOT in your python scripts. And remember that it must be the same Python executable that you used to build ROOT with.
Cheers,
Vincenzo