According to the documentation here, this should create a python2.7 virtual environment (29 April 2021) with spyder installed. I verified that spyder version 3.3.6 is python2.7 compatible
conda create -y -n py27 python=2.7 spyder=3.3.6
However, I could not run spyder in the py27 environment due to conflicts that conda failed to catch. The workaround shown by asanganuwan on  this Spyder Github Issue page worked for me also
Found a workaround to use Spyder on python 2.7.
setup two virtual environments for Python 2.7 and 3.6.
Launce anaconda navigator and install spyder 3.3.6 on both the environments
Launch spyder on the environment with Python 3.6
Preferences-->Python Interpreter --> set the Python path for 2.7
Restart Spyder
Done!
So my recommendation is next run
conda create -y -n py36 python=3.6 spyder=3.3.6
conda activate py36
spyder
And follow the last three instructions from asanganuwan.
Also you should use the conda package manager as much as possible since it is smarter with managing requirements. When I try to use pip install spyder after activating the environment, it warns of version conflicts and fails to start.