TOTP/HOTP hasn't changed for years. The app works perfectly for me and needs no updates.
I use it on ios, and so does most of Red Hat employees (they state it is a preferred version of tfa over the google app.)
It's not broken for the 15 or so accounts I use it for.
Try the "scan code" button which should activate the camera and the app will crash. I just tested it with my iPhone and verified. The iOS App Store application was last updated 4 years ago. There's also comments there saying it doesn't work anymore.
Reading / using existing codes might work properly, or manually inputting them.
Interestingly my wife's XS is having the problem you describe but not my X.
I've sent a note to the maintainers, but there's an open git issue for it. Not sure when their commits will roll to the store.
I'm told by multiple colleagues at redhat that they've raised this with internal support, so it should be sorted eventually. Lots of iphones in redhat and this is the app they officially support for TFA internally.
Nope. I used that feature just today to add another account. Works on my iPhone X.
Also, the last commit to the app was a year ago, if you head to their github page.
It's abandonware these days and hasn't been updated for years. The iOS app doesn't work anymore and can't use the camera for reading codes.