Not sure about Damus because I'm allergic to Apple products, but I'm pretty sure Primal supports it on Android. I can't be sure because I can't remember how I signed in way back when I first installed it.

Apple doesn't have any good external signing options as far as I know. One of the Apple devs should consider building one, though not nostr:nprofile1qqsr9cvzwc652r4m83d86ykplrnm9dg5gwdvzzn8ameanlvut35wy3gpz3mhxue69uhhyetvv9ujuerpd46hxtnfduq3qamnwvaz7tmwdaehgu3wwa5kuegpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43q3ttcfs because he's already testing the bounds of time with all the amazing stuff he's working on. There's only so many hours in the day!