You can list all installed programs by running the following command. Note that it will produce a lot of output since it includes even small utility programs so you might want to dump the contents to a file to narrow things down.
sudo apt list --installed
# Will create a file called all_programs.txt with the contents
sudo apt list --installed > all_programs.txt
# Narrow down the results if you are looking for a specific program(s)
sudo apt list --installed *{gimp,writer,connect}*
There are some other programs installed as flatpaks, a different package format, which you can list using another command:
# Use the -a option to list all installed programs
flatpak list -a
# Use the -d option for details
flatpak list -ad
Or if you prefer a graphic interface you can install Synaptic package manager which will allow you to see the same information. I don't know if it will actually detect and list flatpaks though.