Seeking lightweight open source BI software

It depends on the Data architecture and the complexity of your requirement. Some great tools in the market are Qlik sense, Power BI, OBIEE, Tableau etc. I have recently started using Cognos Enterprise and some of the features that come with this version and the ease to create Dashboards/Explorations/Story Boards are really great. One thing to watch out for is the Cost for Cognos Enterprise and if cost is not an issue, I feel Cognos Enterprise is worth trying.

There are many...It would rather depend what System BI architecture or Enterprise legacy you have at your end...I would recommend as follows: 

1) If you have legacies of SAP, Oracle  - look for SAP BI (including Excelcius) and OBIEE respectively. Both of them have their own flavour of Dashboard, Information Semantics, Macro Intelligence Universes - with all the features of data drill, user created function developments etc...in built. Pros - Robust, Cons - You need a good practice team to configure your requirements.

2) If you are on MS platform, you can try Power BI. The desktop version is good, rich in features and much at ease with native SQL Server ecosystem 

3) If you have licenses for Tableau, Qlik or Pentaho BI, all of them are equally competitive for the requirements that you have mentioned. Your decision would depend on the licensing investment that you would consider.

4) Self Sustained BI tool - MicroStrategy comes with great features and I have used MicroStrategy for some time.

There are multiple options in Cloud as well...in AWS , I have used Quicksight and been able to drive few reporting requirements that you have mentioned.

I've worked on Power BI and OBIEE. I mostly prefer OBIEE, as it has an overall solution to most of the problems addressed or seen in developing reports.

The best and open source (No cost involved) solution for all BI requirements is Jaspersoft Open Studio.

Refer to rajeshsirsikar.com for more information.

I advise you to try OneStream. This is a very good platform focused on reporting, consolidation and budgeting & forecasting.