Magnetism is always blamed as the factor causing these negative health effects

Better get rid of all loudspeakers then.
Even a stupid lightbulb has a magnetic field that influence you more than a solar flare.

Most of the papers I read on this mention “Schumann resonances”, and sometimes “pineal gland” crystals.

Probably to dupe the gullible and uninformed with technical terms.
These people are probably either con-men or mentally ill.

en.wikipedia.org/wiki/Schumann_resonances

Schumann resonances are the principal background in the part of the electromagnetic spectrum[2] from 3 Hz through 60 Hz

These frequenceies are very close to many other everyday phenomena, occurring in music (loudspeakers) and light-bulbs as previously mentioned.

my.clevelandclinic.org/…/23334-pineal-gland

secretes the hormone melatonin. Your pineal gland’s main job is to help control the circadian cycle of sleep and wakefulness by secreting melatonin.

So why is the main function of the gland unaffected? Also there is very little reason to believe these alleged “crystals” would be magnetic.

It consists of small crystals that are less than 20 µm in length

20 µm is very small.
From the above link about Schumann resonance:

These correspond to wavelengths of 38000, 21000, 14000, 11000 and 9000 km.

There is NO WAY these 2 can resonate together, simply NADA possibility. There is a factor of 1 billion distance between them being able to resonate!