AFAIK there is no virtualization possible under OCLP....
This is certainly not true. But depending on what software you use and what you're trying to run there can be problems. Some versions of parallel uses the Metal API to accelerate parallel's own program drawing, and if you have no Metal support, the parallel program runs unsupported instructions and crashes.
You can use VMWare or VirtualBox, and if these programs do not use Metal API to draw its own program interface, you won't run into a problem there.
But MacOS starting with Catalina banned kexts, which is traditionally how many virtualization programs (on the host) implement certain acceleration functions. So older virtualization programs trying to install kexts because they were developed for older MacOS and were allowed to install kexts at the time would refuse to work. For instance, you will need VirtualBox 7.0 on Monterey host because older VirtualBox may refuse to start.
Then when we are talking about guests, if you're running macOS as a guest (on an Intel based host), anything after Catalina cannot have graphics accelerations, due to kext restrictions.
So virtualization on MacOS is possible, but severely restricted. I can confirm the following combination works: Monterey 12.7 host + VirtualBox 7.0.4 + Ubuntu 22.04 guest