Howdy Double-A,
Let's stick with the current topic of "hard alternative".
That's a fairly broad subject, but one that's worth exploring imo. And I don't really see another recent thread with a similar topic. Except for this more general one, which is probably also worth checking out...
https://www.head-fi.org/threads/exp...ethereal-wave-etc-appreciation-thread.807227/
There are definitely a few alternative artists (including some punk/post-punk) with a harder
edge there,... which is the way I'm going to interpret this topic.
I haven't heard some of the newer bands mentioned here. I think some of mikeofearth's suggestions are pretty good though, based on a quick sampling of some of the groups' tracks. His suggestions lean a little more toward the ambient side than Nirvana and RHCP though. So the latter may be a little easier to "rock out" too.
RHCP's
Blood Sugar Sex Magik (and their music in general) is a blend of different styles, principally punk-rock and
funk. But with elements of metal and hip-hop thrown in (Anthony often "raps" his lyrics, for example). And probably also a bit of psychedelia as well (think Doors and Hendrix). I'm pretty sure they were/are George Clinton/P-Funk fans, like many of the gangsta rappers in the 80's and 90's.
In terms of "old-school" rock bands (and I'm talkin like the 70's and 80's), I'd suggest groups like Iggy Pop & the Stooges, and David Bowie, rather than Aerosmith and Metallica. I have nothing against metal. And even like quite a bit of it... But Iggy and David get closer to an alternative vibe.
After those guys, you might try groups like Joy Division/Warsaw, Peter Murphy/Bauhaus/Love & Rockets, Siouxsie & the Banshees, Echo & the Bunnymen, The Smashing Pumpkins, and NIN. Some of these may be a little too "gothic" for your taste, but they all do pretty good stuff. And certainly fit the criteria of "hard" and "alternative".
I'll put my thinkin cap on, and try to come up with some other harder-edged groups that might be a little more the flavor of RHCP and Nirvana though. And will post as they come to mind, along with anything else I can think of.