Hello,
Motivated by the need to migrate from ubuntu20.04 to ubuntu24.04 on our cluster in order to install v9.1.0, we looked into other solution to manage our packages and avoid relying on distro packages.
Spack appears to be a nice solution and we manage to create an openTelemac package that allows to build openTelemac from v6p3 up to 9.1.
It requires many patches but it works great!
This package will be shared later, it requires a bit of cleaning before make it public. It will be very specific to our cluster config but with some little work it could be generalized if someone want it to land in spack package repo.
Compared to a compilation based on packages from ubuntu20.04 (gfortran, openmpi, metis, python, …), [name removed] based compilation reduce computation time by up to 20%!! We didn’t perform a complete benchmark but 1 model reduced from ~1h to 40min, another 1 from 6h to 4h50mn.
Hope someone will find this interesting! 
Feels free to ask any questions.
[name removed]