CentOS

As Trevor said:
"Now repeat that command for the largest directory and keep doing that until you find the bottom level directory that uses all the space. Now review that to see if the contents of that are required."

And:
8151 /var
42023 /usr
I.e. 8 and 42GB.

Apart from what Trevor says:
It looks like this is a quite new system, so CentOS 7 may not support the CPU/GPU/etc.

CentOS 8 or CentOS Stream 8?
CentOS 8 died at the end of 2021 and if you're using CentOS 8
then it probably doesn't have Qt_5.15.3. You could look into
converting into Rocky or Alma which do have 5.15.3.

Not surprising if you don't have a network connection:
Download it on another machine, transfer it and then use rpm to install it.
And if you have network, first install ELRepo.

Is it a long time since you have rebooted? - a new kernel requires a reboot.
Also, CentOS 7 dies in three months time.

Deleted - didn't see Trevor's answer.

What's your RAID cards?

And if security is a concern, then Stream may not be the best choice:
Stream is a rolling pre-release (aka. beta) of the next RHEL point
release. It may be better to use one of the RHEL clones/rebuilds like
Rocky, Alma, OEL etc.

Looks like it's missing, on a fully updated system I have gstreamer1-plugins-bad-free from April 2018.

I guess Trevor already gave you an answer, you have to check your repo-files.
Alternatively output from yum update may help.