I installed the package libmypaint1.3.0 on my debian 10 system. I can tell it is installed because when i run the command sudo apt-get install libmypaint-1.3.0 the system responds with "libmypaint-1.3-0 is already the newest version".
It also says "libmypaint-1.3-0 set to manually installed", which i do not know how to interpret. Nevertheless, if i run the command pkg-config --exists --print-errors "libmypaint >= 1.3.0" i get the message "No package 'libmypaint' found" (and exit status 1). I would like to fix this, but i don't want to do a frankendebian on my system, especially so soon after i set it up about 10 days ago . . . Oh -- and as to why i want pkg-config to see the package, that's because i'm trying to build some software that's checking dependencies using pkg-config, and the check seems pretty reasonable to me . . . TIA for any info or advice. dan