Shared Web Hosting
WordPress, PHP and MySQL are better supported and have more documentation available in Linux versus Windows environments. Hosting with SSH access is used for SFTP access and testing of Cron jobs.
Ubuntu 18.04 LTS
Originally selected as easy to use and stuck with it. An LTS (Long Term Support) version is used to avoid frequent upgrades; non-Ubuntu package sources often provide more recent versions of software for LTS versions of Ubuntu.
More client software and hardware drivers are available on Windows than other operating systems. Keep current for best available security, but use Stardock Start10 to provide Windows 7 Start button.
Windows Server 2019
VPS when Windows is required
Consistent with Windows 10 user interface.