Is possible to improve the activation time of a conda environment?

Not that it matters how long it takes to activate an Anaconda environment as long as it is within 2 minutes. However, as a person using both Linux and Windows with Anaconda, I can say that activating environments on Windows takes significantly longer than it does on Linux. Given that my Windows machine is also much more powerful than my Linux machine (gaming desktop vs. standard laptop) and that I have more and bigger environments on Linux, I am pretty sure it simply has to do with the Windows version of Anaconda or Windows itself.

You might want to try just expanding your path, if you just need a program out of your conda environment, e.g. in your .bashrc or .zshrc:

export PATH=~/miniconda3/envs/my-env/bin:$PATH

That takes like no time. If you need more out of the environment though, try the other options.

I suspect that conda just does packages freshness check when it starts, over the internet.

In your condarc, try to set

auto_update_conda: False

If that does not help, also try

offline: True

(See the docs.)