Hello,
after an install fails, please check if "/tmp" directory contains files starting with "avast", especially either something like avastpostinstall-1578309388-51133.log, avastinit-1578391808-1998.log, avastuserinit--1578390810-myusername-91035.log. Please send these files to ondrej.kolacek <at> avast.com
Kind regards,
Ondrej Kolacek