Here is the output,
$ sudo apt install -y mssql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
mssql-server : Depends: libjemalloc1 but it is not installable
Depends: libc++1 but it is not installable
Best Answer
This is because both of those packages are in the Ubuntu Universe, to enable that repository you can use,
Note that the Universe Packages are not Officially Supported by Canonical and the Ubuntu Team, but instead by the community. For more information see the Security FAQ