Best Linux server with Hardware to use for mid size business

My suggestion would be a Dell PowerEdge as far as hardware goes. There are multiple options for various budgets. I can even recommend buying a used one from a reputable reseller.

Software-wise, my first pick is Debian 64-bit; it is very stable, easy to update, and has a large number of free software packages for it. It will support print and file services, active directory via Samba 4 if you want to use a Windows domain with Windows desktops, and even DNS and authentication services. You do not even have to install a graphical user interface if it will be managed solely over the network, but if it makes the server administrator more comfortable to control the server locally, there are various desktop options available for free.

Naturally, there are many hardware/software combinations; these are only my recommendations based on personal experience.

Here are some Linux servers with hardware that are suitable for mid-size businesses:

1. Dell PowerEdge R740: The Dell PowerEdge R740 is a powerful and versatile server that is ideal for mid-size businesses. It features the latest Intel Xeon Scalable processors, up to 3TB of memory, and up to 16 2.5-inch drives. It also supports various Linux distributions, including Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Ubuntu Server.
2. HPE ProLiant DL380 Gen10: The HPE ProLiant DL380 Gen10 is a popular server that provides high performance and scalability. It features the latest Intel Xeon Scalable processors, up to 3TB of memory, and up to 24 2.5-inch drives. It also supports various Linux distributions, including Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Ubuntu Server.
3. Lenovo ThinkSystem SR650: The Lenovo ThinkSystem SR650 is a reliable and flexible server that is suitable for mid-size businesses. It features the latest Intel Xeon Scalable processors, up to 3TB of memory, and up to 24 2.5-inch drives. It also supports various Linux distributions, including Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Ubuntu Server.
4. Supermicro SuperServer 6029P-E1CR12L: The Supermicro SuperServer 6029P-E1CR12L is a high-performance server that is ideal for mid-size businesses that require a lot of storage. It features the latest Intel Xeon Scalable processors, up to 3TB of memory, and up to 12 3.5-inch drives. It also supports various Linux distributions, including Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Ubuntu Server.
5. IBM Power System AC922: The IBM Power System AC922 is a powerful server that is ideal for mid-size businesses that require high-performance computing. It features IBM Power9 processors, up to 2TB of memory, and up to 12 2.5-inch drives. It also supports various Linux distributions, including Red Hat Enterprise Linux, SUSE Linux Enterprise Server, and Ubuntu Server.