There are definitely more diverse funding sources available for deep tech but mostly if you limit "deep tech" to more traditional physical domains like hardware, biotech, medtech, etc. For domains like computer science, the non-traditional deep tech funding sources tend to be few outside US intelligence agencies.
That said, having raised capital for software deep tech, I think the best path forward today is to position it as a SaaS startup. The execution strategy is quite different than a traditional SaaS startup and requires significantly more front-loaded personal investment on the part of the founders, but I think it is a lower hurdle to clear in terms of effectively raising investment than positioning as deep tech.
My own view is that as an industry we are currently quite poor at fostering the formation of software deep tech startups (which is an opportunity). This is both because they are difficult, unusual startups from an investor perspective and there are very few entrepreneurs with experience successfully executing this type of startup. Thousands of articles exist on executing and investing in SaaS or consumer tech companies, and approximately none for software deep tech.