With the exception of a few unique stations here in there, true alternative is doesn't really exist. Yes, you have stations like Alt 98.9 in LA or Radio 105.7 in Atlanta but these stations are largely focused on 90s and active/alternative cross-overs. The only true alternative stations out there that are not independent would be The Buzz out of Kansas City owned by Entercom.
The Edge is not what it use to be, especially after the corporate sounds of IheartRadio took over. I'll be honest, the Buzz (Houston not Kansas City) is nothing to run home about either.
I've always praised 105.7 The Point in St. Louis as the best possible approach. During the day, they lean active with lots of 90s. You will hear the harder 90s and early 2k stuff like Three Days Grace, Manson and Korn. At night, the station focuses more in the alternative direction hitting currents hard and breaking new music. This tends to be the newer music of the alternative variety vs active.
They also bring concerts that range anywhere from Slipknot to Band of Horses. Their facebook page use to get a lot of hate but at the end of the day, the station is positioned to lean in both active and alternative, depending on time of day and frankly, what is working across all rock stations. The station has the active and alternative space blocked. For example, recently, iheart launched an alternative station in St. Louis. It sounds like all the other iheart alt stations with the same 100 songs being played over and over. The Point kicks their a$$ because The Points playlist includes lots of deeper cuts both 90s alternative, harder rock and new stuff.
Cumulus Alternative stations are a little better to me than Ihearts but generally speaking, iheart radio's alternative stations are Alt 40, meaning, it's the chart toppers on the alt charts and true alternative folks have went elsewhere. Personally, I listen to three different outlets: Alt Nation, WEQX, and The Buzz out of Kansas City. I'm not 100% sure on this but Active Rock doesn't appear to be doing well at all.