I don't think mycelium is greatly secure for ios...
OP is looking for signing a message using bech32 address from ios. I think that must not be something to be concerned for such security unless they hold a big fund in that certain address OP want to import private key.
You could steal their identity using it though and that's clearly something they're trying to do here... Either for staking an address or confirming an identity on another site...
I dont have an iPhone because I can't afford it
Just get an older version :-P
People think apple is too luxury :-D
I don't think they're luxury, I think they're owned by novices of technology and people whow want less control over customisation and personalisation... But if you need it for compatibility reasons then that's acceptible (I have an apple product just in case I have to run anything that won't run on android, Windows or Linux)...