I finally asked Salesforce support, thanks to them they've been very good on this case.
Here is the answer :
There are two different causes for this:
Custom report types behave differently from our standard report types when it comes to how roles of users are handled and what
Opportunities are visible to certain users. Please have a look at this
I guess you are filtering on the wrong field. Segment (API Name Segment__c ) is the field on the Account object. while you are entering the id of Segment record which is an independent object record hence it showing the blank report.
you can create the joint report
account with the opportunity
Account with the client segment
the second report type will ...
What worked for me: Added newly created fields to the Report Type
The fields had been added to the object after the report type was created, so I had to add the fields to the report type.
How I added the fields to the Report Type: Salesforce > Setup > Home tab > quick search for and choose 'Report Types' > Click on the report type name > ...
If you don't mind static graphs (i.e., not interactive, you can still dynamically generate them), you could look at https://quickchart.io/ which allows you to create graphs images given a bunch of JSON parameters
It only shows how many times a particular Cloud Page was viewed. As it is based on the standard Web & Mobile Analytics collect code, no other metrics are captured.
Clicks are not collected, as those would require the outbound links to be redirected through tracking links (as is the case for links coming from emails).