autosummary emits broken links if `primary_domain` is not `py`

[astrojuanlu]

Describe the bug

autosummary expects the primary_domain to be py. Otherwise, it gives warnings like these:

WARNING: Unknown interpreted text role "obj".

for each .. autosummary:: directive.

In the HTML documentation there are broken links with the text

:obj:`get_random_ingredients <lumache.get_random_ingredients>`
:obj:`InvalidKindError <lumache.InvalidKindError>`
:obj:`lumache <lumache>`

for every .. autosummary:: directive.

How to Reproduce

(TBC)

Expected behavior

I would expect autosummary to work regardless of the primary_domain configuration.

Your project

(TBC)

Screenshots

OS

Linux

Python version

3.9.7

Sphinx version

4.2.0 and earlier

Sphinx extensions

No response

Extra tools

No response

Additional context

This was originally reported in #2001, but it was not sufficiently well described and was perhaps prematurely closed.