I have a driver to contribute, I have found the official ESS Solo-1 driver online for Windows 3.11 but unfortunately the package was awful (wrong folders, random autoexec.bat file) and the installer was broken despite coming from the official archived website.
Attached is a .zip file I put together that contains the official ESS Solo driver, but with an older installer exe taken from the ISA ESS AudioDrive and everything restored to the proper locations. This will allow the driver to install if you first load the ESS Solo dos driver. It provides WAVE and MPU support to Windows 3.11.
I have also included the ESS AudioRack that was part of the ESS AudioDrive driver bundle I took the install exe from.
This should allow other ESS Solo-1 owners to more easily use this card on Windows 3.11 as I am not aware of any other working install packages for this card that support 3.11.
The archive.org link can be found here : https://archive.org/details/essolo-311