Fatal Python error: init_import_size: Failed to import the site module

Problem

I am running Ubuntu 20.04 LTS. I have both Python 3.8 and Python 3.9 installed, although Python 3.8 is broken.
When I type the command python3.8 into my terminal I get the following:

root@ubuntu-3pl:~# python3.8
Fatal Python error: init_import_size: Failed to import the site module
Python runtime state: initialized
Traceback (most recent call last):
  File "/usr/lib/python3.9/site.py", line 79, in <module>
    import os
  File "/usr/lib/python3.9/os.py", line 29, in <module>
    from _collections_abc import _check_methods
  File "/usr/lib/python3.9/_collections_abc.py", line 12, in <module>
    GenericAlias = type(list[int])
TypeError: 'type' object is not subscriptable

That to me looks like python3.8 is digging around in /usr/lib/python3.9, which is python3.9's library.
Here is the output of a few commands:

root@ubuntu-3pl:~# which python3.8
/usr/local/bin/python3.8
root@ubuntu-3pl:~# which python3
/usr/bin/python3
root@ubuntu-3pl:~# /usr/bin/python3 --version
Python 3.9.5
root@ubuntu-3pl:~# python3
Python 3.9.5 (default, Nov 23 2021, 15:27:38) 
[GCC 9.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

Python 3.9 works just fine, but Python 3.8 obviously does not work. I want Python 3.8 to work because I want to install landscape-common and various other packages which rely on it. This is what happens when I try to install landscape-common:

root@ubuntu-3pl:~# apt install landscape-common
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  bc distro-info-data iso-codes libpython3-stdlib lsb-release python-apt-common python3 python3-apt python3-attr python3-automat python3-cffi-backend python3-click
  python3-colorama python3-configobj python3-constantly python3-cryptography python3-gdbm python3-hamcrest python3-hyperlink python3-idna python3-incremental python3-netifaces
  python3-openssl python3-pkg-resources python3-pyasn1 python3-pyasn1-modules python3-service-identity python3-six python3-twisted python3-twisted-bin python3-zope.interface
  python3.8
Suggested packages:
  isoquery python3-doc python3-tk python3-venv python3-apt-dbg python-apt-doc python-attr-doc python-configobj-doc python-cryptography-doc python3-cryptography-vectors
  python3-gdbm-dbg python-openssl-doc python3-openssl-dbg python3-setuptools python3-pampy python3-qt4 python3-serial python3-wxgtk2.8 python3-twisted-bin-dbg python3.8-venv
  python3.8-doc
The following NEW packages will be installed:
  bc distro-info-data iso-codes landscape-common libpython3-stdlib lsb-release python-apt-common python3 python3-apt python3-attr python3-automat python3-cffi-backend
  python3-click python3-colorama python3-configobj python3-constantly python3-cryptography python3-gdbm python3-hamcrest python3-hyperlink python3-idna python3-incremental
  python3-netifaces python3-openssl python3-pkg-resources python3-pyasn1 python3-pyasn1-modules python3-service-identity python3-six python3-twisted python3-twisted-bin
  python3-zope.interface python3.8
0 upgraded, 33 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
Need to get 6362 kB/6410 kB of archives.
After this operation, 41.2 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python3.8 amd64 3.8.10-0ubuntu1~20.04.2 [387 kB]
Get:2 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 libpython3-stdlib amd64 3.8.2-0ubuntu2 [7068 B]
Get:3 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 distro-info-data all 0.43ubuntu1.9 [4744 B]
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Get:5 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-cffi-backend amd64 1.14.0-1build1 [68.7 kB]
Get:6 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-netifaces amd64 0.10.4-1ubuntu4 [16.1 kB]
Get:7 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-pkg-resources all 45.2.0-1 [130 kB]
Get:8 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-six all 1.14.0-2 [12.1 kB]
Get:9 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 iso-codes all 4.4-1 [2695 kB]
Get:10 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python-apt-common all 2.0.0ubuntu0.20.04.6 [17.1 kB]
Get:11 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-apt amd64 2.0.0ubuntu0.20.04.6 [154 kB]
Get:12 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-gdbm amd64 3.8.10-0ubuntu1~20.04 [15.2 kB]
Get:13 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 bc amd64 1.07.1-2build1 [86.3 kB]
Get:14 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-attr all 19.3.0-2 [33.9 kB]
Get:15 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-automat all 0.8.0-1ubuntu1 [27.5 kB]
Get:16 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-constantly all 15.1.0-1build1 [8244 B]
Get:17 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-idna all 2.8-1 [34.6 kB]
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Get:19 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-incremental all 16.10.1-3.2 [14.9 kB]
Get:20 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-zope.interface amd64 4.7.1-1 [85.2 kB]
Get:21 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-twisted-bin amd64 18.9.0-11ubuntu0.20.04.1 [11.1 kB]
Get:22 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 python3-cryptography amd64 2.8-3ubuntu0.1 [211 kB]
Get:23 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-openssl all 19.0.0-1build1 [43.3 kB]
Get:24 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-pyasn1 all 0.4.2-3build1 [46.7 kB]
Get:25 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-pyasn1-modules all 0.2.1-0.2build1 [32.9 kB]
Get:26 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-service-identity all 18.1.0-5build1 [10.7 kB]
Get:27 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-hamcrest all 1.9.0-3 [24.9 kB]
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Get:29 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-configobj all 5.0.6-4 [34.1 kB]
Get:30 http://azure.archive.ubuntu.com/ubuntu focal-updates/main amd64 landscape-common amd64 19.12-0ubuntu4.2 [86.4 kB]
Get:31 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-colorama all 0.4.3-1build1 [23.9 kB]
Get:32 http://azure.archive.ubuntu.com/ubuntu focal/main amd64 python3-click all 7.0-3 [64.8 kB]
Fetched 6362 kB in 0s (22.5 MB/s)    
Extracting templates from packages: 100%
Preconfiguring packages ...
Selecting previously unselected package python3.8.
(Reading database ... 123547 files and directories currently installed.)
Preparing to unpack .../python3.8_3.8.10-0ubuntu1~20.04.2_amd64.deb ...
Unpacking python3.8 (3.8.10-0ubuntu1~20.04.2) ...
Selecting previously unselected package libpython3-stdlib:amd64.
Preparing to unpack .../libpython3-stdlib_3.8.2-0ubuntu2_amd64.deb ...
Unpacking libpython3-stdlib:amd64 (3.8.2-0ubuntu2) ...
Setting up python3-minimal (3.8.2-0ubuntu2) ...
/var/lib/dpkg/info/python3-minimal.postinst: 5: py3compile: not found
dpkg: error processing package python3-minimal (--configure):
 installed python3-minimal package post-installation script subprocess returned error exit status 127
Errors were encountered while processing:
 python3-minimal
E: Sub-process /usr/bin/dpkg returned an error code (1)

I installed Python 3.8.0 from https://www.python.org/ftp/python/3.8.0/Python-3.8.0.tgz. Here is the result of compgen -c python:

root@ubuntu-3pl:~# compgen -c python
python3.8-config
python3.8
python2
python3.9
python2.7
python3.9-config
python3
python
python2
python3.9
python2.7
python3.9-config
python3
python

Question

How can I either:

• Uninstall all traces of Python 3.8 and successfully reinstall it?
• Fix it so that it runs?
• Install landscape-common using Python 3.9?

Any help/advice is very welcome! I am happy to try anything aside from reinstalling the OS.