Do I need to add my workplace's 401k assets to my solo 401k's assets to determine if I need to file form 5500? What about my IRAs, are those "one participant plans"?

Workplace is my 9 to 5 job with standard 401k plan. I also have a solo 401k for my freelance work. And I have my IRAs. I think I just need to make sure that any solo 401k assets (I only have 1 solo 401k) are under $250,000 and I don't need to file form 5500, but not 100% sure. Do IRAs not count as "one participant plans"?