I like the UI of Aurora (purple teal logo). I don't remember why, but I paid for Pro. I also have alerts on my phone from the site https://aurora-alerts.uk/ There's of course the NOAA website but the UI isn't as smooth or I just don't know what I'm doing. Aurora has a nice prediction map that's updated every few minutes. Aurora-alerts/Glendale has good alerts when it detects storm bursts. On 10/10, it alerted me ~20 minutes prior to each of the 3 bursts.

Honorable mention to Aurora Notifier (black green logo). It's map isn't as helpful as Aurora, but it incorporates usergsubmitted settings by location. When Europe has a ton of green dots, I know the activity is at least producing aurora