Is there an alternative to Electrum ? Is it possible by example to use a wallet that is validated by the appstore ? By example, I have seen Trust Wallet but maybe there are other best alternative ?
You can never be absolutely sure, being "validated" by a company doesn't mean there can't be bugs in it or malware on your system.
There are many alternatives, but Electrum is often recommended. It also comes preinstalled on Tails, which makes offline signing much easier.
The thing is... Electrum comes pre-installed with Tails, but it is not the latest version. So if you update Tails on a "Persistent Volume" to the latest version of Electrum, then you effectively void the benefit of having a clean boot every time you use that "Persistent Volume"? (Asking, because I do not know)
I have swept many coins from Paper wallets to Electrum without any problems..... but I guess I have just been lucky. I am still looking for a program that can encrypt a "Private Key" offline and then when it goes online.... that program decrypt it and sweep the keys.