While running "make debs" to build Lustre codes on Ubuntu 22.04, debhelper tool suite reported the following warnings:

dh_clean: warning: Compatibility levels before 10 are deprecated (level 9 in use)
dh_installdeb: warning: Compatibility levels before 10 are deprecated (level 9 in use)
......

According to http://man.he.net/man7/debhelper, the current recommended compatibility level is 11.