To clarify a few points:

- Just because you’ve used the same device for other crypto without issues doesn’t mean it’s safe as some malwares targets specific types of keys, backup files, .. etc.

- Testing with small amounts doesn’t guarantee safety as some hackers might target larger sums instead.

- Avoiding installing suspicious apps or files isn’t a foolproof way to ensure safety as there are many seemingly legitimate apps that can still compromise your data even screenshots and saved files thats include any data in your clipboard (I might share a topic related to this)

- Whether Coinbase is a good option or not isn’t the main focus here the OP topic is about moving his father's coins from a paper wallet to Coinbase since he is already a user of Coinbase I assume he is familiar with the exchange and wallet rules and knows how to use it <correct me if my assumption is wrong>

It’s important to note that not all hot wallets are compromised, not all devices are hacked, and not every online method is at risk <I use Blue and similar options on my iPhone almost daily for couple of years and I have never been compromised> However, there is a potential risk of exposure when using them without a solid understanding of security practices if you believe you have thoroughly evaluated your device security and you are confident that it's secure you can consider using the Blue wallet option but if you’re unsure about your device security it’s best to stick with the safer options suggested by LoyceV.