See config\configsets\ametys-standard\conf\managed-schema
The managed-schema is big, and contains some business fields.
Why do we not have here a very simple managed-schema, with only, let's say, the id field ?
As the first thing to do in Ametys is to click on "Global Indexation" which will start to send schema (with updates from all Ametys plugins, etc.), then the schema will be good.

I believe the probleme is for the CMS tests. Thus probably the issue is just the CMS (search) tests which do not send schema at first, or something like that.

So very easy to fix in my opinion, the hardest thing is to check nothing is broken.