Patterns provider is always set to the base_plugin_definition provider

Attached is a patch impolementing the proposed resolution

The patch work for me. Many thanks auth.

Changing to major as it really is important to pick up custom patterns, borderline critical as it breaks the parts of a site without this patch.

Hello guys,

Thanks for your contribution. The issue you met may be a side effect of 🐛 Fix views preview when pattern declared by ui_pattern_library in the front theme. Fixed

I would not do the review myself, because this subject is a bit tricky to me. I am afraid if we fix one stuff here, we will have a side effect somewhere else.

Is applying the patch on your project good enough for now?

I have been struggling with this same issue and finally found #2 patch works for me!

My error was:
Uncaught PHP Exception Twig\Error\LoaderError: "Template "modules/contrib/ui_patterns/modules/ui_patterns_library/templates/pattern-page-body.html.twig" is not defined." at /code/web/modules/contrib/ds/templates/ds-entity-view.html.twig line 10