I did find nunchuk, it seems to work on android, fine. Anyone has iphone that can confirm you can use signet there? It's under Profile, then Network Settings.
Discussion
Signet seems to work fine on nostr:npub1cvqlzvmjercdn0ypsmv8f7j9lge6ahsnueh5rparh53wuswftv4q49yjt3 . There is an issue, however, where the default server signet.nunchuk.io:50002 is not intended for public use, so signet is only publicly useful if you manually change the network setting to a public server, like: ssl://mempool.space:60602
I found this issue report on github that indicates this default server will be changed to a public one in the next release... that was like 4 releases ago. 🤷
https://github.com/nunchuk-io/nunchuk-android/issues/74
Sorry if this is all old news... I just now ran into this issue myself and came across your thread... I thought it might be worth adding what I found so far.