,I bought a new laptop (HP ProBook) that I set up as dual-boot: Debian Buster 10.2 amd64 (with W7 on the side). I'm trying to install QMMP 1.1.6 as opposed to the current 1.2.6. 1.1.6 is no longer available on the QMMP web site, but I copied the /var/cache/apt/archives/qmmp_1.1.6-1.1_amd64.deb file from another machine, putting it in the same directory on my laptop.
I tried using apt install (using SU) to install it, but it says it's not there. I had better luck with dpkg -i /var/cache/apt/archives/qmmp_1.1.6-1.1_amd64.deb; at least it found the .deb. But I get two warning messages: 'ldconfig' not found in PATH or not executable; and 'start-stop-daemon' not found in PATH or not executable. I checked; they are both in root's PATH and have the executable flag set.
If you were wondering, I've found qmmp 1.1.6 easy to use. The newer version breaks my music list into categories (ugh!) instead of the flat A-to-Z list I'm used to; and the UI is so dark it's hard to read. I'll consider this problem resolved when QMMP 1.1.6 is successfully installed and usable.
I checked on the internet and on SE, but all I found was how to use DPKG, not how to fix this particular problem.
I still have QMMP 1.2.6 installed on my laptop, but it never got as far as complaining that I'm attempting to replace the current version with an earlier one.