I'd really like to see a truly open alternative on the mobile space. The biggest issue is the hardware. It's just not standardized and there's no incentive to do so. It's really preventing the way Linux took off on developers desktops back in the late 90s/early 2000s. FirefoxOS and Ubuntu Touch looked promising, but they lacked good hardware to run on. I'd really like to try Plasma, but I don't like any of the device…
I really want PostMarketOS to succeed, for one because it would be really neat to have an open phone OS but also because I think it would cut down a lot on the number of phones that end up being demolished long before their actual life-span is at an end.
It's about as responsive as my Pixel (i.e. not very responsive, not even close to iPhone) and it's a great size.
The problem is, as always, the battery. If I could replace that and install PostMarket, I might use it as my daily driver.