You can add the line showExperimentalOptions=true to the [General] section in the nextcloud.cfg file. The file is located in /home/yourusername/.config/Nextloud. After adding this line the option for Virtual Files should appear in the UI, when you add a new account.
However, apart from a short test when the feature was relatively new, I have no experience with it and can’t tell you how well it works in practice. But there are definitely some limitations compared to Windows, where as far as I understand it, uses some native Windows features in order to provide this functionality.