Earlier quoted context omitted.
If the A18 Pro has the same ISA as the M-series chips then this may not be so straightforward. I am still hanging on to my 2020 Intel MBP for dear life because it is the only Apple device I own that allows me to run Ubuntu and Windows 11 on a VirtualBox VM.
As long as you're ok with arm64 guests, you can absolutely run both Ubuntu and Win11 VMs on M-series CPUs. Parallels also supports x86 guests via emulation.
Also is it possible to convert an existing x86 VM to arm64 or do I just have to rebuild all of my software from scratch? I always had the perception that the arm64 versions of Windows & Ubuntu have inferior support both in terms of userland software and device drivers.