I wouldn’t worry. As others has said in this thread; a way more powerful magnet is present inside the HDD. Also fans produce magentic fields to a small degree.
Then again, I don’t store anything important on the magnetic drive in my PC, so I’m not risking anything. 🤷♂️
I have one in my case, attached to the metal part covering the PSU in a CM silencio case. I have a single 2.5" hdd in the same case, without any issues.
I have OTP codes backed up on an old Android media player from Fiio.
If my (or family's) devices break, I usually order parts from a local dealer, that's usually delivered the next day, and then I dig into a repair.
For repair jobs that takes longer, or a device is entirely borked, I have a few old phones kicking around, that can be used.
In danish it means shit.