I tried to install the Emulator in this VM but, as you said, it doesn't work. This is not an issue for students that have already upgraded to Catalina/BigSur, as they have more powerful macs where they can run a HighSierra VM I setup to them to run Scratch 1.4. Upgrading to BigSur is not an option to them, as the other app they need to use for their test is Scratch 1.4, a 32bits app. My fear is that, when the exams will get closer, many more students will raise the same problem. I don't know much about HighSierra and Mojave, except for one single student unable to install it.
The Emulator runs fine on Windows 10 and on macs running Catalina and BigSur. During tests students are not allowed to use their smartphones, so the Companion is not an option. However, during this lockdown year, tests are remote so that students have to use their computers at home.
The standard setup is the offline AI2Live with the Emulator running on Windows PCs in a lab. My students for their tests have to develop (simple) App Inventor projects. Ubuntu/arm64 can run inside the QEMU emulator. What is the reason behind this really non-standard setup? Using Android Studio, this was as easy as opening up the Android SDK.