Install fenicsx v0.9

Hello community,

The new version of FEniCSx v1.0 was recently released, and I was wondering how to install version v0.9 on Ubuntu with conda or apt? Since I need to continue working with that version.

Instructions for installing with apt (ubuntu) are given at Download | FEniCS Project
The debian packages are not yet upgraded to v0.10, so if you install them now, you can hold them at the 0.9 versions.

Is it no longer possible to use Conda?

You can specify versions when installing with conda, see for instance FEniCS-workshop/environment.yml at d50da6fce99da55a1a0090c360030c2790baffb0 · jorgensd/FEniCS-workshop · GitHub
where it shows how to pin to a specific release, or set an lower bound (one can also set upper bounds)