Update the custom env recipe to correctly activate it by default

[mathbunnyru]

Describe your changes

Issue ticket if applicable

Fix: #1903

Checklist (especially for first-time contributors)

• I have performed a self-review of my code
• If it is a core feature, I have added thorough tests
• I will try not to use force-push to make the review process easier for reviewers
• I have updated the documentation for significant changes

[mathbunnyru]

@creative-resort please, check, if this works for you.

[mathbunnyru]

3.8 also works fine.
I updated these lines to make sure 3.10 also works.
And this recipe will stay up-to-date a bit longer (till 3.10 reaches eol).

[mathbunnyru]

I've checked it on my machine and it seems to work well.
@creative-resort please, tell me if you encounter any issues.
I will merge this PR (and close the issue), because I will need this updated recipe to fix another issue as well.