I have the exact same issue with Logitech keyboard K520 and Ubuntu Server iso 15.10
It looks like an issue with alternate iso as it is working with Linuxmint installer (which - I think - is based on Ubuntu desktop 15.10)
(I tried that because the desktop installer is not handling my fakeRAID correctly!)
I did not find any recent bug related to this issue, any idea? Any workaround (I have been looking for an other keyboard to make the installation but I don't have PS2 or other USB anymore!)
I have the exact same issue with Logitech keyboard K520 and Ubuntu Server iso 15.10
It looks like an issue with alternate iso as it is working with Linuxmint installer (which - I think - is based on Ubuntu desktop 15.10)
(I tried that because the desktop installer is not handling my fakeRAID correctly!)
I did not find any recent bug related to this issue, any idea? Any workaround (I have been looking for an other keyboard to make the installation but I don't have PS2 or other USB anymore!)