When and why did ftp break in some browsers?

[StephenG1CMZ]

I just read in this thread that ftp no longer works in some browsers.
https://www.hpmuseum.org/forum/thread-16883.html

I thought I'd ask about it here to avoid cluttering up that thread.

For what it's worth, it works on:
Iphone's safari browser, and
Firefox on Android's Google Play
(the ftp show a list of zips at least - I've yet to try downloading them).

On Android's Chrome, it hangs or goes slow.

At least it's not just HP Prime emulator functionality that disappears.

But what's gone wrong with ftp, and why?
And if you have to choose an ftp app rather than simply use your browser, how do you choose one that's safe?