Allegra had no network cable and no mouse. We found Allegra'snetwork cable (black) and connected it.
I found a dirty old school mouse and connected it.
I wiped Allegra and now I'm currently installing debian 10 on allegra following Jon's elog.
04/01 update: I forgot to mention that I tried installing cds software by following Jamie's instruction: I added the line in /etc/apt/sources.list.d/lscsoft.list: "deb http://software.ligo.org/lscsoft/debian/ stretch contrib". But this the only thing I managed to do. The next command in the instructions failed.
deb http://software.ligo.org/lscsoft/debian/ stretch contrib"