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Can't install tensorflow on ubuntu 20.04.3 Python 3.6.15 pip 21.2.4

I have been around the mulberry bush for a few days trying to get tensorflow installed on an Ubuntu system. My specifications are;
Ubuntu: 20.04.3
Python (virtual environment): 3.6.15
Pip: 21.2.4
Tensorflow version wanted: 1.13.1
Tensorflow version will take: anything at this point
I followed a number of answers on the web. Got a compatible version of Python. Got the latest pip....
When I use the command;
pip3 install tensorflow==1.13.1
I get;
ERROR: Could not find a version that satisfies the requirement tensorflow==1.13.1 (from versions: none)
ERROR: No matching distribution found for tensorflow==1.13.1
when I do a pip_search on tensorflow, it shows tensorflow 2.6.0.
But when I do;
pip3 install tensorflow==2.6.0
I get the same error.
when I use the --upgrade switch to pip, I get the same error. I tried to install from a wheel file, but the file was incompatible on my system.
Any help is appreciated.

As per documentation of Tensorflow, version 1's final release that can be downloaded/installed is 1.15. Below this version are deprecated and no longer available to use in development.
Read it about here

Having trouble installing mediapipe

I have:
macOS Mojave version 10.14.6
python 3.8.3
pip 21.1.3
pip install mediapipe
py -m pip install mediapipe
…
all give the following two errors:
ERROR: Could not find a version that satisfies the requirement mediapipe (from versions: none)
ERROR: No matching distribution found for mediapipe
Also what does version refer to? pip, python , mediapipe?

Note: To make Mediapipe work with TensorFlow, please set Python 3.7 as the default Python version and install the Python “six” library by running pip3 install --user six.
https://google.github.io/mediapipe/getting_started/install.html

Not sure if still relevant but I was running into this issue on an M1 MacBook Pro and the issue seems to be that mediapipe doesn't have an Apple silicon version. Note all the releases for mediapipe are x86/x64:
https://pypi.org/project/mediapipe/#files
I found a fix here, someone compiled it for silicon: https://github.com/google/mediapipe/issues/3277
Basically,
pip install mediapipe-silicon

I can't install opencv-contrib-python with pip

Occured probrem
I ran the following command to install an older version of opencv-contrib-python (4.0.0.21). Then an error occurred and this package could not be installed. How can I resolve this error?
pip install opencv-contrib-python==4.0.0.21
Collecting opencv-contrib-python==4.0.0.21
ERROR: Could not find a version that satisfies the requirement opencv-contrib-python==4.0.0.21 (from versions: 3.4.8.29, 3.4.9.31, 3.4.9.33, 3.4.10.35, 3.4.10.37, 3.4.11.39, 3.4.11.41, 3.4.11.43, 3.4.11.45, 4.1.2.30, 4.2.0.32, 4.2.0.34, 4.3.0.36, 4.3.0.38, 4.4.0.40, 4.4.0.42, 4.4.0.44, 4.4.0.46)
ERROR: No matching distribution found for opencv-contrib-python==4.0.0.21
Environment
Windows 10
Python 3.8.2
Pip 19.2.3

The version you specified opencv-contrib-python (4.0.0.21) does not have a relevant python3.8 version.
You need to use opencv corresponding to python3.8, or lower your python version to match the opencv version.

pip using out of date package index

I am trying to install package inside a docker container(python:rc-slim).
As of now I see that most recent azureml-core wheel uploaded to PyPI is:
azureml_core-1.13.0-py3-none-any.whl
but when I run pip install azureml-core==1.13.0 I get following error:
ERROR: Could not find a version that satisfies the requirement
azureml-core==1.13.0 (from versions: 0.1.50, 0.1.57, 0.1.58, 0.1.59,
0.1.65, 0.1.68, 0.1.74, 0.1.80, 1.0rc83, 1.0rc85, 1.0.2, 1.0.6, 1.0.8, 1.0.10, 1.0.15, 1.0.17, 1.0.17.1, 1.0.18, 1.0.21, 1.0.23, 1.0.30, 1.0.33, 1.0.33.1, 1.0.39, 1.0.41, 1.0.41.1, 1.0.43, 1.0.43.1, 1.0.45, 1.0.48, 1.0.53, 1.0.55, 1.0.57, 1.0.57.1, 1.0.60, 1.0.62, 1.0.62.1, 1.0.65, 1.0.65.1, 1.0.69, 1.0.72, 1.0.74, 1.0.76, 1.0.76.1, 1.0.79, 1.0.81, 1.0.81.1, 1.0.83, 1.0.85, 1.0.85.1, 1.0.85.2, 1.0.85.3, 1.0.85.4, 1.0.85.5, 1.0.85.6, 1.1.0rc0, 1.1.1rc0, 1.1.1.1rc0, 1.1.1.2rc0, 1.1.2rc0, 1.1.5, 1.1.5.1, 1.1.5.2, 1.1.5.3, 1.1.5.4, 1.1.5.5, 1.1.5.6, 1.1.5.7)
When installing packages from 'apt-get' I usually have to update the index first but I can't find a comparable command to do that with pip.

azureml-core version 1.1.5.7 supports Python 2.7 and 3.4+.
Starting from version 1.2.0 it only supports Python 3.5+.
From your list of versions I can guess you use Python 2.7 or 3.4. To use a later version of azureml-core you need a later version of Python.

Two possibilities:
the package needs you to use an underscore (since hyphens don't behave) so pip can download it: so run pip install azureml_core==1.13.0
Run with the --no-cache-dir argument, so pip install --no-cache-dir azureml_core==1.13.0. This argument forces pip to refresh it's package cache.

Installing tensorflow-data-validation with pip installation

I have tried to install tensorflow-data-validation 0.9.0 with pip installation, but it keeps giving me the same error: Could not find a version that satisfies the requirement tensorflow-data-validation...
isn't this version available for windows or i am just missing something?

From the PyPi documentation on tensorflow-data-validation you can see the version compatibility:
Requires: Python >=2.7,<3
So you won't be able to install it with other versions (like your 3.6.2).