The best alternative to Parallels Desktop is WinBoat, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Parallels Desktop and ten of them are so hopefully you can find a suitable replacement. Other interesting alternatives to Parallels Desktop are QEMU, Boxes, MiceWine and Awingu.
Runs Windows applications, individual apps, or full desktops inside Linux with native OS-level integration, sleek interface, advanced filesystem sharing, smartcard passthrough, and resource monitoring while supporting simple installation and ongoing feature updates.
QEMU, an open-source hypervisor, performs hardware virtualization, emulates CPUs using dynamic binary translation, and supports various architectures. It runs diverse unmodified guest OS, provides device models, and offers mixed translation modes for efficient execution.
QEMU by itself is built into macOS, but it's a pain to run (it's all command-line) unless you use a GUI wrapper like UTM. It's also slower than Parallels due to limited support for hardware accelleration.
A simple GNOME application to access virtual systems. It is based on a design from Jon McCann and Jakub Steiner.
I'm not sure you can actually run Boxes on macOS, but from my experience running it on Linux, it's more comparable to UTM than to Parallels, and UTM is built specifically to run on macOS.
MiceWine is a project that aims to run Windows applications and games on Android smartphones.
Awingu provides an online workspace, available through any browser. The online workspace make legacy apps, SaaS and files available in a highly intuitive way.
Using Wineskin technology, Porting Kit is a PaulTheTall.com app that can install games and apps compiled for Microsoft Windows® in Mac OS X. It has access to a server where we store WSI files for more than 300 games, which can be installed by any Porting Kit user.
GDaaS is GPU Desktop-as-a-Service. A Cloud Platform that deploys powerful vGPU-accelerated cloud desktops delivering mobility and collaboration to engineers and designers.
FAUmachine is a virtual machine, similar in many respects to VMWare[tm], QEMU or Virtual PC[tm]. What distinguishes FAUmachine from these other virtual machines, are the following features:
Romania
EU
France
Czechia
Netherlands
Belgium
Germany
I think WinBoat is the best alternative to Parallels Desktop because it works the same way, with a similar workflow and an interface that's just as beautiful and user-friendly.