I used Yahoo to follow along with some Giants games this season -- I just kept my phone propped up on a table while doing other things. Like Go90 last year, it's a pretty good service. But, yeah, not having an easy way to get it on a TV sucks.
Having niche events like this is how streaming services are going to build out a following. It's why ESPN is going after mid-major college basketball, rugby and cricket to fill out its ESPN+ line-up. I imagine Yahoo (or is it Oath now?) was willing to pay up the way traditional TV networks weren't, if any traditional TV networks bid at all.
The real money in this competition is the after the first round, when MLS teams start playing Liga MX teams. And then, it's probably only the semis and finals.