Add hint that users may need to use something else than apt if they are on some other distribution

Signed-off-by: DL6ER <dl6er@dl6er.de>

docs/ftldns/debugging.md

@@ -31,7 +31,7 @@ Once you are used to it, you can skip most of the steps. Debugging *FTL*DNS is q
 
 ## Prerequirements (only required once)
 
-1. Install `screen` and `gdb` using `sudo apt-get install screen gdb`
+1. Install `screen` and `gdb` using `sudo apt-get install screen gdb` (you may need to use another package manager, e.g., `yum`, `dnf` or `apk add`, depending on your distribution)
 2. Start a screen session (it will allow you to come back even if the SSH connection died)
     * If you don't know about `screen`, then read about it (you *will* love it!)
 3. Start a screen session using `screen`