I have been able to install Cube Explorer today on a very up to date M1 macbook air with Monterey.
Just double clicking the HTM (half turn metric not html) version of cube explorer did not work. It would say "waiting for XQuartz to be installed" and not progress.
In PlayOnMac I went to Install a program.
In the lower left corner I went to "Install a non-listed program"
click through a few time then I chose "install program in a new virtual drive"
Named my drive (ALGDEPO in my case"
Left the next page with three options blank
Chose a 64bit windows instalation
When asked to choose an installer browsed to "cube514htm.exe" the Half turn metric version of cube explorer
Let Cube Explorer generate it's tables and such. Checked "allow slice moves" and let it generate even tables.
Quit cube explorer
When it asked "Please choose a file for PlayOnMac to use for a shortcut" I chose browse and browsed back to "cube514htm.exe" again. It's still on the mac drive, it hasn't been moved to the virtual drive.
After choosing I'm taken back to the choosing page again. Hit Cancel.
Now I have an installed app I can use. When I open PlayOnMac it's listed there. The desktop shortcut doesn't work however.