I'm trying to add a filter on project type, but it does not appear to work. According to this article, the field projectType should be queryable. Note: I have admin access to the org and have a Standard Jira Software license.
Sounds odd, given the docs, but try dropping the "" around "software".
The other thing to try is letting the autocorrect do the work for you - go to the advanced search and belt in "projectType = ", then start typing softw... it should start making suggestions, including software, which you can then select and let Jira do the rest of the selection work.