I can't install missing packages for firedrake

[handraqui]

I'm trying to install firedrake on Ubuntu 20.04.6 LTS the command python3 firedrake-install.

python3 firedrake-install
Running firedrake-install
Checking for presence of package build-essential...
missing.
[...]
Checking for presence of package libopenblas-dev...
missing.
Installing missing packages: build-essential, autoconf, automake, bison, flex, cmake, gfortran, git, libcurl4-openssl-dev, pkgconf, libtool, libxml2-dev, python3-dev, python3-pip, python3-tk, python3-venv, zlib1g-dev, libboost-dev, libopenblas-dev.
Lendo listas de pacotes... Pronto
Construindo árvore de dependências       
Lendo informação de estado... Pronto
Alguns pacotes não puderam ser instalados. Isto pode significar que
você solicitou uma situação impossível ou, se você está usando a
distribuição instável, que alguns pacotes requeridos não foram
criados ainda ou foram retirados da "Incoming".
A informação a seguir pode ajudar a resolver a situação:
Os pacotes a seguir têm dependências desencontradas:
build-essential : Depende: libc6-dev mas não será instalado ou
libc-dev
Depende: g++ (>= 4:9.2) mas não será instalado
gfortran : Depende: gfortran-9 (>= 9.3.0-3~) mas não será instalado
libboost-dev : Depende: libboost1.71-dev mas não será instalado
libtool : Depende: libc6-dev mas não será instalado ou
libc-dev
libxml2-dev : Depende: libicu-dev mas não será instalado
python3-dev : Depende: libpython3-dev (= 3.8.2-0ubuntu2) mas não será instalado
Depende: python3.8-dev (>= 3.8.2-1~) mas não será instalado
zlib1g-dev : Depende: libc6-dev mas não será instalado ou
libc-dev
E: Impossível corrigir problemas, você manteve (hold) pacotes quebrados.
apt-get not found or disabled. Proceeding on the rash assumption that your compiled dependencies are in place.
Please use the --show-dependencies for more information.
Creating firedrake venv in '/home/users/.../firedrake'.
Traceback (most recent call last):
File "firedrake-install", line 1724, in <module>
check_call([python, "get-pip.py"])
File "firedrake-install", line 666, in check_call
log.debug(subprocess.check_output(arguments, stderr=subprocess.STDOUT, env=os.environ).decode())
File "/usr/lib/python3.8/subprocess.py", line 415, in check_output
return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
File "/usr/lib/python3.8/subprocess.py", line 516, in run
raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['/home/users/.../firedrake/bin/python', 'get-pip.py']' returned non-zero exit status 1.
Install log saved in /home/users/.../firedrake-install.log

It checks for presence of several packages, proceeds to install them, reads the trees of dependencies, reads "state information" and tell me that some packages couldn't be installed.

Trying to solve this by following what I found on the web, I tried lots of things: Installing build-essential, but it depended on libc6-dev. Tried to install libc6-dev, but it depended on libc6. Tried to install libc6, but it's already installed, in an older version. I don't know how to downgrade it and actually I'm worried about the consequences of such downgrade. Every trial comes with a message like "impossible to solve problems, you held broken packages" (translating from Portuguese).

I am really clueless about it. I'm installing it in my workstation only a couple weeks after I installed in my personal notebook successfully, and I really don't know why is that.

I also tried to use aptitude, but was careful to still not downgrade anything. I don't know what to do about petsc. In Firedrake download tutorial, it says that one thing you might try to do is to install manually the dependencies before trying to install firedrake. But I couldn't figure out how to install each of those, for example a Fortran compiler, since the system already has one.

Also, here's the log:
firedrake-install.log