All most half of bitcoin users secure their wallet on smartphone and computers which is very easy for thief to access the wallet, if not properly secured. The best way to secure your wallet is having alternative devices where you can keep you wallet safe and your private key and don't keep the devices with you maybe you can keep it in bank.
It is ideal if you are using a wallet which is the use of the full potential by the owner its not ideal to use a wallet like you cannot handle most of the transactions you made such as fees, and other security features. The alternate device you are talking about is the hardware wallet such as ledger, trezor etc. Currently, im using a trezor which is ideal to use but if you don't have a budget yet there's an application to use such as the electrum they have their executable file and apk too.
There are a lot of wallets available in the market and one of it is the hardware wallet which i think is the safest one to use. But it depends on your own preference as every user has its own set standards. You can read it here..
https://e-cryptonews.com/what-are-the-safest-ways-to-store-bitcoins-in-2021/However, even if you have the safest wallet to store your bitcoin, if you are not responsible from making it safe and secure at all times, then you will still lose everything you have in your wallet.