>> It seems to be this thing:
>>
https://www.notebookcheck.net/Review-Iomega-eGO-Portable-500GB-USB-3-0.33106.0.
html
>
> It's spinning rust drive, that is going to be slower as main OS disc
> than any sort of flash based medium. It would be OK for mass data storage.

Go with the spinning rust - you might be surprised at the performance.
Some people seem to think you always need the very fastest. It all depends
on what you are planning to do.

>> I tried to plug it in just now, while the Pi 4B was running with power
>> from the wall socket, and it crashed the operating system. The X-server
>> crashed, it returned to the text console, and then seemed to lock up
>> with some kind of file system errors being printed. It accepted no input
>> from the keyboard anymore.
>
> It probably requires too much power, and caused a voltage dip. You'll
> need to use a USB hub to provide the power most types of spinning rust
> hard drive require.

Quite a lot of modern spinners work perfectly well powered from Raspberry
pi's. You do need an adequate power supply. And for the 4B that means one
that supply 3 amps.

> Given the two points above, it's the wrong thing for a Raspberry Pi. If
> you are happy with the its physical form factor, get a USB attached SSD.

"wrong thing" - how prescriptive. In 2 of my Pi cases USB attached
spinning rust turned out to be the right point re. price/performance.
Let's be a bit more nuanced about this.

--- SoupGate-Win32 v1.05