(using default cube)
In 2.8 edit mode I couldn’t find Extrude_to_Cursor on the Mesh menu.
I read the manual and it says CTL-LMB - same as most tutorials - but I forgot that in 2.80 this is of course now CTL-RMB. This works fine, especially in quad spilt views mode (CTL-ALT-q).
So, other Newbies, I do recommend RTFM - but beware the change from RMB to LMB and vice-versa, the manual hasn’t caught up yet!
CASE CLOSED thanks