You can check the installation guide from DirectAdmin’s website:
We highly recommend a processor of at least 500 Mhz even though DirectAdmin will run on slower systems. The more cores the better. A minimum 1 GB of memory is required (2+ GB is preferred), with at least 2 GB of swap memory. (CentOS 8: 2Gig required, 4+ Gig preferred). A hard drive with at least 2 gigabytes of free space (after the Linux install) is also required, not including any website data. If you are expecting high traffic levels then you will need more memory, processor power, and hard drive space than we recommend here. Intel and AMD should work fine. Solaris/Sparc will not.
Operating systems supported by DirectAdmin are listed in the table below.
CloudLinux (recommended) 6.x 32/64-bit, 7.x 64-bit, 8.x 64-bit
RedHat Enterprise / CentOS 6.x 32/64-bit, 7.x 64-bit, 8.x 64-bit
Debian 8.x 64-bit, 9.x 64-bit, 10.x 64-bit, 11.x 64-bit ALPHA(click for Ubuntu)
FreeBSD 11.x 64-bit, 12.x 64-bit
More information can be found here:
Hope that this helps!