This website is lacking a link to the UBoom L firmware and it is not good to try to find it using Google search. A link that I found on Google has it, but why should I trust someone that is not Earfun? Why should I trust the link? Why should I trust any of the files?
The instructions on the Google searched website / Google Drive are mostly in Chinese. The images are in Chinese. Professional documentation is lacking. A simple purchae of Snagit will let you get the job done in other languages such as English and with images in the selected language.
This site needs a secured folder (HTTPS and FTPS) that is on Earfun server.
Quite simple and yet not here on the "Support" page. This should be addressed ASAP.