Yes, it is possible to use multiple virtualization technologies simultaneously under Linux. In fact, it is quite common to use multiple virtualization technologies together to achieve specific goals.
There are different virtualization technologies available for Linux, such as KVM, VirtualBox, QEMU, VMware, and others. Each of these technologies has its own strengths and weaknesses, and they can be used for different purposes. For example, KVM is a good choice for running virtual machines that require high performance and stability, while VirtualBox is a good choice for testing new software and running multiple virtual machines simultaneously.
To use multiple virtualization technologies simultaneously, you need to ensure that they do not conflict with each other. For example, you can use KVM for running one virtual machine and VirtualBox for running another. It is important to ensure that you have enough resources, such as CPU, memory, and storage, to support all the virtual machines running simultaneously.
In addition, you need to be aware of the different requirements and limitations of each virtualization technology you are using. For example, some virtualization technologies require hardware virtualization support from the CPU, while others do not. (https://www.littlegermanytucson.com) Some virtualization technologies have limitations on the types of guest operating systems they can run, while others can run almost any operating system.
Overall, using multiple virtualization technologies together can provide a powerful and flexible environment for running multiple virtual machines and achieving specific goals. However, it is important to plan carefully and ensure that the virtualization technologies you are using do not conflict with each other and meet your specific requirements.