See [this stackoverflow question](https://stackoverflow.com/questions/30170468/how-to-run-spyder-in-virtual-environment) which refers to [this official reference here](https://github.com/spyder-ide/spyder/wiki/Working-with-packages-and-environments-in-Spyder).

1. Spyder should be installed in the base environment.
2. Activate the target environment (e.g. `conda activate py39a`).
3. Install `spyder-kernels` (e.g. `conda install spyder-kernels`)
4. find and copy the path for the python executable inside the environment (`python -c "import sys; print(sys.executable)"`)
5. deactivate the environment (e.g. `conda deactivate`)
6. run Spyder
7. Spyder→Tool→Preferences→Python Interpreter→Use the following interpreter→paste the environment python executable path.
8. Restart the ipython console.