Same, for both my current and previous. The two before that were via a recruiter relationship. Before that was through a friend who works there, and before
that was a de facto apprenticeship, also via a friend already there. I have never gotten a job in this industry by submitting a resume cold. From this I conclude that the point is not to need to.
You need the LinkedIn profile to look good both to humans and to robots, and a worthwhile recruiter will give you substantial help tuning both that and your resume because these will both help them place you, which is how they get paid. Make sure a new recruiter clearly understands this and is happy that you clearly understand it, too. Those who fail this test are not the ones you want to work with.
It will be harder to work with top-tier recruiters if you're working your way up and not yet established. That's not fair, but it's the way of the world, and as always you mistake the ought for the is at your peril. If you're smart and capable, just not yet tested and proven, the ideal is to find a recruiter who will invest in helping you develop. This is tricky and I lucked into it. The best advice I can offer there is, bigger firms with deeper pockets are more likely able to support that.
The unequivocally good news is that there is a lot of interest, money, and good roles sloshing around the market right now. While that's less good for a newer junior than for a proven senior, it is still good for us all.
Don't wait. The article compares the tech industry labor market to the housing market, which I think is accurate. It also compares now with the boom before the 2000-2001 crash, and I think that is accurate too. We can reasonably predict another crash. We cannot reasonably predict when. So get while the getting is good.