you have a typo in “affected”

One is probably link local the other is global, that’s pretty normal. https://en.wikipedia.org/wiki/IPv6_address#Address_Scopes

Ah okay, it’s a user unit then. Try the following:

$ systemctl --user enable ydotoold
$ systemctl --user start ydotoold

Sadly very typical for science journalists.

It looks like you’re missing the ydotool.service unit file in the package. Can you check by running dpkg -L ydotool-custom (the name of the package you chose in step 3.4)?

Unit files are how services are defined in most Linux-based desktop systems, similar to services in Windows.

can you explain the joke, i work at cloudflare

Also if you make a typo you can quickly fix it with ^, e.g.

ls /var/logs/apache

^logs^log

Except solar. And wind. And hydro.