It is okay and safe to some degree to try using the Opera mini browser wallet to store your coins. It is just that Opera mini since I have known, is a browser app. The latest technology breakthrough in Web3 and Blockchain has sure triggered a ripple effect of change across major platforms that has been used to having an online base of customers patronizing their services.
Opera mini sure has taken a cue, and Op, if you do try using their wallet, let us know.
Otherwise, it is advised to do as others have done and use a major wallet service provider like Electrum which has proven to be rather reliable than others.
Also, Opera mini wallet is an open source wallet according to the FIO protocol it uses.
Just do the necessary KYC verification and biometrics and try to remember your key phrases, for any new wallet you use.
You can access the Opera Crypto Wallet by downloading Opera’s Crypto Browser. You can download it here.
To set up the wallet, click the wallet icon on the left sidebar. You can set up a new wallet or restore your existing wallet with your recovery phrase.
https://help.opera.com/en/crypto/opera-wallet-integration-guide/The FIO Protocol is an open-source, decentralized usability solution that works across all blockchains, and uses human-readable Crypto Handles (e.g. hello@opera) to replace the complexity, risk, and inconvenience of transacting with long-string public wallet addresses.
https://blogs.opera.com/mobile/2022/03/opera-fio-protocol-crypto-wallet-handles/