Update:
VirtualGL 3.0, with the new EGL back end, was released in November of 2021. The EGL back end still has some known application compatibility issues, however, so any outside testing (particularly with commercial applications) is appreciated.
An EGL/X11 front end was developed between November, 2021 and January, 2022 and is now available for testing in the dev/3.1 evolving pre-release of VirtualGL. EGL/X11 support is necessary when running recent versions of Firefox or Chrome using VirtualGL.