Good thing indeed, thanks for the report! Glad to hear it works again, although I am looking forwards to our own apps to be independent from third-party shenanigans like this one.
We obviously don’t provide the proprietary Yubico management applet, and we don’t indent to provide something API-compatible either.
So is the current Yubico version working for Apex Flex users? It’s still not working for me, but maybe I’m running an old version of the OTP applet and I need to reinstall.
I’ve confirmed that the latest version for Android is working, and based on the bug fix and user reports, I believe the now fixed bug affected both iOS and Android.
Finally sat down to do some testing. Destroyed and reinstalled the OTP applet and also installed HMAC-SHA1. Yubico happily works with my Apex Flex on Mac and Windows, but still instantly crashes the latest iOS app. Eagerly awaiting the new app from you guys. 
I also deleted the OTP applet and reinstalled the newest version and it works perfectly with Yubico Authenticator 1.11.1 on the iPhone 12 running iOS 18.4.1.
Is there a formal place to request features? Specifically applet versions. It might be helpful to diagnose future issues.
Applet versions are implemented now but you can only see what version the applet is if you manually send an APDU command to the applet or use Apex Manager on Android (it will show the app versions). The iOS version of Apex Manager is coming soon and it will also show the applet version.
Okay, I was able to get Yubico’s app to work, but I had to uninstall my FIDO2 applet to do it. Now it scans without crashing.
whaaa? if you install fido2 does it crash again?
Need to dig up my old Android to test that. Getting the bogus “not enough space” error trying to reinstall FIDO2 on iOS. Only TOTP and a handful of keys are installed now.
Any update on a release for the iOS app?
Didn’t Amal mention that the iOS applet was expected to be released in May? I can’t find anything about it on the forum, has it not come out yet?
yes… yes I did… then things got jiggled pretty hard. We are circling back to iOS development soon™
