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 corporation doesn't mean there can't be bugs in it or malware on your system.
There are many alternatives, but Electrum is usually recommended. It also comes preinstalled with Tails, which makes offline signing much easier.