Well, step 1 is don't die. Step 2 is don't suck.
So you have to account for survival first. If you need to get a job, then get a job. You don't need to find a fulfilling passion until step 1 is taken care of.
Also, I think it's important to differentiate between work and passion. Most people never discover an alignment between what they do to earn money and what's most important to them. Instead, most people become passionate about something like their family and work is just something they do to support their passion. It's normal to not find a startup you're passionate about.
A pattern I've seen described, that might work in your case, is to ask your clients if they have any unsolved problems they would happily pay you money to solve. Use their responses as the basis of your search. Keep paying the bills, and in your "spare time" investigate these problems. If one of them grabs you, ask for payment up front, if you get it, then you've found alignment between a passion and work.
An alternative approach is to look for people who are a little bit ahead of you and going in the direction you want to go. People who have found an alignment between their passion and work, and who are a little ways into the journey. Shop among them for one that you want to join. Work on their passion and find out how it's going for them.
Another alternative is to dramatically alter the survival equation so that you can devote yourself to exploring potential passions without worrying about survival. Live super cheap; maybe move to Vietnam or something.
For context, I found an alignment between my passion and work. At least, I hope I did. One person's asked to pay for it already, I just have to get that part built. I never followed a pattern of trying to find a passion I could turn into an income, I just always chased down and tackled interesting challenges. A while ago realized that the solution I'd come up with had way too much potential to remain a hobby. Now I'm in a place where I'd rather fail at this new thing than succeed at my day job.
If that's the kind of feeling you're looking for then try to tackle problems that are standing in the way of things you believe should happen. I was trying to apply the principles of open source software projects to hardware projects and just couldn't personally accept that they weren't working. It started to infuriate me. I could picture all the great things that would come from open source hardware, but none of us could come up with a way to make the process work, so none of those great things could happen. It felt personal. I don't think you're going to find that kind of personal, emotional, passionate connection to run of the mill business problems.