possible to add it as dropin too: cp /etc/xdg/autostart/welcome.desktop ~/.config/autostart/
and edit file as user nano ~/.config/autostart/welcome.desktop or use your prefered editor…
Since no information was given by the OP, let me give this as a possible solution. Not Likely, but possible.
If the missing “Missing Mirrors option” is on an ARM device, that option will not appear in Welcome as ARM devices use a totally different set of mirrors.
Pudge
Sorry. I posted before I re-read the OP. After doing so, I realize this is a different problem.
I guess I picked the wrong week to stop drinking coffee.