When you install software from the Debian repository, it does not always come up with the latest version. It adjusted with its own software release schedule. Any latest software usually comes first into testing/unstable categorisation, if already mature, the maintainer will move the specific version of the software into a stable release which will be readily available with
apt install.
Debian repository does have the latest version of
Electrum 4.4.6, but it hasn't yet on the stable release, so you need further configuration to install the latest version.
I suggest instead of changing your system-wide installation sources, you better manually install Electrum with its own installation tutorial. Go to
https://electrum.org/#download, on "Installation from Python sources" go ahead with "Install with PIP:"
sudo apt-get install python3-pyqt5 libsecp256k1-dev python3-cryptography python3-setuptools python3-pip
wget https://download.electrum.org/4.4.6/Electrum-4.4.6.tar.gz
wget https://download.electrum.org/4.4.6/Electrum-4.4.6.tar.gz.asc
gpg --verify Electrum-4.4.6.tar.gz.asc
python3 -m pip install --user Electrum-4.4.6.tar.gz
If after running the above command, you type `electrum` on the terminal and it does not open up. You need to add up a few configurations.
Open bashrc file with nano or any text editor.
On the last line of the file append
export PATH=~/.local/bin:$PATH
Save then exit. You should be able to run it now.