I assume you want Virtualmin installed. It will correctly configure everything you need, including PHP-FPM.
Ubuntu 26.04 is technically supported, though it is currently available only as a Grade B system. It will move to Grade A with our next release.
You can install it using:
sudo sh -c "$(curl -fsSL https://download.virtualmin.com/virtualmin-install)" -- --bundle LAMP --os-grade B --branch unstable
However, if you want to install PHP-FPM, you can follow our guide, which also works for Webmin-only installations.