Supplementaries has been split into AMENDMENTS, so there does not seem to be a supplementaries:wall_lantern and supplementaries:wall_soul_lantern in the supplementaries.
I have sent a suggestion to the AMENDMENTS side to fix it because both lanterns are wall_lantern in the AMENDMENTS, and the color coding is not possible. But it was negative response :(

Can the following comments be fixed on the Solas Shader side?
MehVahdJukaar/amendments#229 (comment)

It's not exactly a clean solution, but after some trial and error, you can add amendments:wall_lantern:light_level=10 to the #Soul Torch, Soul Lantern, Soul Campfire, Soul Fire section of block.properties and it does split it. However if any mod or command modifies light levels of lanterns it does break it again.

There is probably a better way to do this, I just don't know how right now.