This is possible, and fairly easy. With 12.3, which recently was released, there will be the ability to upgrade your components, which will include a new landing page and new simplified reports and navigation. So you may want to check that out!
To point to a different landing page, follow these steps:
Go to your tables and filter on "Hidden"

You should see a table called "Params"

You will check this table out and then convert it to an editable table by navigating to the "Source" Step in the transform pipeline and then click "Enter Manually"

In the next dialogue choose "Blank Table". It won't wipe out the existing content, just make it editable.
Now you can go to the table step and click in the InitialReport column and update this text to point to a new landing page. You can just type the value in on the screen and save the change.

The actual text you put in the "InitialReport" can be tricky to get right. My recommendation is to create your landing report at the top of the report hierarchy and try just replacing the "Service Costing" text with your new report name. Another tip, if this doesn't work, is to look at your new landing page and try to make sense of the URL text and look at everything starting with ".View". For example this part of the report URL:
".View%253Atab%253ATBM+Review"
resolves to ".View:tab:TBM Review"
which informs what to enter in the "IntialReport" column.
Once you save this update to the params project and check it in, your users should be greeted by your new landing page!