This used to work until very recently (I'm 97% sure it worked a month ago).

I have a server where in my home
  /home/aacid
there is a symlink to another folder
aacid@annarchy:~$ ls -l
lrwxrwxrwx 1 aacid freedesktop   33 May 21  2016 poppler_web -> /srv/poppler.freedesktop.org/www/

If i go to that server using dolphin+sftp and click on the poppler_web folder i get

Maybe it's more a kio regression than a dolphin one?

Could not read the file sftp://poppler.freedesktop.org/home/aacid/poppler_web.

This used to work until very recently.

I'm using KDE Applications 18.04 and KF5 5.47