I tried one more time.
Please use the apps gui to update webkitgtk4, reboot and test boincmgr.
If anybody knows how best to configure cmake to force i486, suggestions welcome.
I tried this using -DCMAKE_TOOLCHAIN_FILE: # the name of the target operating system
set(CMAKE_SYSTEM_NAME Linux)
# Which compilers to use for C and C++
set(CMAKE_C_COMPILER /usr/local/bin/i486-linux-gnu-gcc)
set(CMAKE_CXX_COMPILER /usr/local/bin/i486-linux-gnu-g++)
..but webkitgtk wouldn't configure