@anisgh Which version of Debian did you try to install FOG on? I am really wondering what’s going on because the error we see in the output posted doesn’t make sense to me. The package named mariadb-client is available in all current versios of Debian: https://packages.debian.org/search?keywords=mariadb-client&searchon=names&suite=stable§ion=all (for stretch, buster, bullseye, even bookworm and sid!)
Please try installing it manually via apt-get install mariadb-client and see what error you get.
So either you try to install on Debian 11 - then follow what George posted. Or you are using a really old version of Debian and need to update to a later one first.