Ungoogled-chromium can conflict with Chromium, if it is installed, so you should first uninstall it.
To do this, open a terminal and run in it:
sudo apt-get autoremove --purge chromium
The project is in the openSUSE repositories, to install it from there, you would have to perform a series of instructions:
In principle add the repository to the sources.list file running in terminal:
echo 'deb http://download.opensuse.org/repositories/home:/ungoogled_chromium/Ubuntu_Focal/ /' | sudo tee /etc/apt/sources.list.d/home:ungoogled_chromium.list
Then we would have to add the public key by executing in the terminal:
sudo wget -nv https://download.opensuse.org/repositories/home:ungoogled_chromium/Ubuntu_Focal/Release.key -O "/etc/apt/trusted.gpg.d/home:ungoogled_chromium.asc"
Now it only remains to update the system and install it, running in terminal:
sudo apt update
sudo apt install ungoogled-chromium
Using this method, you make sure you keep it updated with each new version, that the project team keeps updating.
On this site, you can obtain information about the program, as well as obtain the binaries to install it manually: