I remember changing/lowering the "version" of your waterfox in about:config tricks it to installing to a compatible version, I'm on a new computer so I try to remember how I did it but I've tried to search it but there's too much waterfox version in there https://snipboard.io/GLOMrY.jpg
I only SS a small part of the window, there's a lot there of that says version 68
whilst some types of legacy extension may be modified for use with Waterfox Current, Waterfox Current is not intended for use with non-modified legacy extensions
I remember changing/lowering the "version" of your waterfox in about:config tricks it to installing to a compatible version, I'm on a new computer so I try to remember how I did it but I've tried to search it but there's too much waterfox version in there https://snipboard.io/GLOMrY.jpg
I only SS a small part of the window, there's a lot there of that says version 68