Hello, @justcoolk

You should be able to run that on a Ubuntu 20.04 / 18.04 droplet.

To install MSSQL (mssql-server) follow these steps here:

• Import the public repository GPG keys:

wget -qO- https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -

Register the Microsoft SQL Server Ubuntu repository for SQL Server 2019:

sudo add-apt-repository "$(wget -qO- https://packages.microsoft.com/config/ubuntu/18.04/mssql-server-2019.list)"

• Run the following commands to install SQL Server:

sudo apt-get update

sudo apt-get install -y mssql-server

• After the package installation finishes, run mssql-conf setup and follow the prompts to set the SA password and choose your edition.

sudo /opt/mssql/bin/mssql-conf setup

Make sure to specify a strong password for the SA account (Minimum length 8 characters, including uppercase and lowercase letters, base 10 digits and/or non-alphanumeric symbols).

• Once the configuration is done, verify that the service is running:

systemctl status mssql-server --no-pager

If you plan to connect remotely, you might also need to open the SQL Server TCP port (default 1433) on your firewall.

Source: official Microsoft documentation

Regarding the .NET core install, you could follow step one form this article here:

https://www.digitalocean.com/community/tutorials/how-to-deploy-an-asp-net-core-application-with-mysql-server-using-nginx-on-ubuntu-18-04

Hope that this helps!
Regards,
Alex