Ask HN: How to find profitable SaaS or Software ideas?

All of us have software ideas and projects we want to work on or currently working on. I know it is said that scratch your own itch and execution matters, yet there seems to wide array of software where CRM, Sales, DevOps etc. type of software made repeatedly and sold for millions year after year.

My question is how to do market research and where do I collect data for software projects? Getting 5-10 or 40 users, although hard, can be done with hard efforts. Making it sustainable seems really hard.

Where do I go about learning user demand and create products that ultimately end users or companies would pay for?

How do I conduct user research? Any tools, tips, methodologies that worked for you?

Thanks.