I would remove the black mass from the PCB and try to treat it from the bottom. The material is very acid and temperature resistant. The values are zero to very little, so I doubt that it will pay off. The technology is called COB or chip-on-board. https://en.wikipedia.org/wiki/Chip_on_board

I did some of them, and they usually contain no PMs. COB is a low-cost technology to reduce costs. Makes no sense to use PMs here. Mostly, they will use Ni instead of PMs and Al bond wires.

It is a realy pain to remove.

This black epoxy is extremely hard and difficult to remove mechanicaly.

Either use air chisel, incinerate or simply leave it alone.