How can I do keyword research if I do not have a website?

To be able to find keyword opportunities in Rank Tracker one has to create a project: the Keyword Research module will be available in the project's navigation panel:

Yet if you do not have a website or your domain is still under development and is not available online, you may create a dummy project for any website you want - google.com or bbc.com etc. and access the keyword research functionality inside that dummy project.

The reason is that the Keyword Research module in Rank Tracker is a separate section which is not tied to the project's domain. One can explore and find suggestions for any topic and get keyword ideas for different niches, regardless the URL that was used as a project's address.