Not sure actually, it should work, what about
https://rpms.litespeedtech.com/debian/enable_lst_debian_repo.sh instead of
http://rpms.litespeedtech.com/debian/enable_lst_debian_repo.sh
Also, what if you get rid of the rpms install?
FROM litespeedtech/openlitespeed:1.7.16-lsphp80
WORKDIR...