You mean DietPi installation script? Theoretically it should work to install plain Debian Buster netinst on a new partition and run our install script afterwards.
Yes @Joulinar, I installed buster netinst and then DietPiinstall script to convert plain Debian into DietPi, as you adviced here.
I did it yesterday for bullseye and bookworm. It seems the only 2 options currently supported. I did not find an older script.
Thanks for your help and advice.
Francisco.