In message ,
writes
On Sat, 9 May 2020 11:07:06 +0100, Ian Jackson
wrote:

All of my favourite (and not-so favourite) Youtube downloaders no longer
work on this XP machine.

Has anyone else got the same problem - or is it just me? Do I have to
resort to a newly-acquired elderly machine running W10? 4K Video
Downloader certainly does work on W10 - but later versions won't install
on XP, and older versions install but don't work).

3D YouTube Downloader's current version (1.19.3 beta) still works fine
with XP... the author updates it reguarly too.

https://yd.3dyd.com/download/

Thanks. I think I've tried (and used it) before). But no go now, with
either 1.19.3 beta 1 or 1.19.2 (neither install nor portable). It tries,
but..........

11:10:32, 3D Youtube Downloader 1.19.3 beta 1
11:10:33, ffmpeg (ext): lavf 57.83.100, lavc 57.107.100, lavu 55.78.100,
lswr 2.9.100, lsws 4.8.100
11:10:33, libcurl (ext): libcurl/7.67.0 OpenSSL/1.1.1d zlib/1.2.11
brotli/1.0.7 nghttp2/1.39.2
11:13:25, #01, Page analysis,
https://www.youtube.com/watch?v=lhmshcrRNno
11:13:25, #01, Opening given Youtube URL...
11:13:25, [curl@044C242C] retrying at 0 after 0 seconds: client error:
Couldn't connect to server (7)
etc.

But, as I've found, Youtube Downloader (as a Firefox add-on) IS one
that's still OK.
https://addons.mozilla.org/en-GB/firefox/addon/youtube_downloader/
--
Ian