I want to suggest a new step

I suggest adding conda to the list of things topgrade upgrades. conda is a very popular environment manager for Python.

Which tool is this about? Where is its repository?

Official docs: https://docs.conda.io

Which operating systems are supported by this tool?

All operating systems on which the conda command is available.

What should Topgrade do to figure out if the tool needs to be invoked?

command -v conda (from bash, cf. https://stackoverflow.com/a/677212/11348232)

Which exact commands should Topgrade run?

I'd say conda update --all -y, but I'm not sure it upgrades all the environments and not only the currently selected one.

I want to suggest some general feature

No.

More information

• Assuming that someone else implements the feature, please state if you know
  how to test it from a side branch of Topgrade : YES