I finally got around to trying Magic Online with wine on Linux. It worked great, only with one hitch: it gives an error about “Failed to create font resource sserife.fot fontname sserife.fon” during install.
Thankfully, I found a workaround: Find a random ttf font in /usr/share/font/truetype. Copy that to:
Now the installer will finish. Gameplay seems to work without a hitch.