I might be off with my suggestion as there is not much background to go off with just 1 paragraph description of the problem. But…

I’d assume Lotus Notes would be modeled as an IT Component(s). Then you could track Applications utilizing this IT Component(s)… From Applications you could track Business Capabilities and Business Contexts affected.    

I created Lotus Notes as a Business Application and then added the various databases as Deployment Subtypes. I’ve done something similar with SharePoint sites and PowerAutomate applications. Another option would be to model them as Microservices. Neither of these examples would be considered ‘best practice’ as there are specific use cases for both Deployments and Microservices, however, this allowed me to model the numerous small applications (most of which were built within business functions without any EA oversight) without consuming Application licences.

It would also be possible to create a Custom Fact Sheet Type, but I felt that was overkill and I wanted to be able to represent interfaces and organisational units against these small apps so it was far easier to keep within the Application Fact Type.

Some of our Lotus Notes Databases or Sharepoint Sites are significant in terms of scale, user base, functionality etc, so for those I create them as a full Business Application and associate then with their ‘platform’ parent.