Humidity control as a cross-species lever.
Diatomaceous earth kills springtails by drying out their cuticle, but the dust stops working the moment it gets damp, and a springtail can't survive anywhere dry. That mismatch decides where the dust is worth using, and where it never will be.
A bedroom has no drain, no trap, nothing you rinse, so springtails on a bedroom baseboard mean water is arriving where you cannot see it. Where they sit in the room narrows that water down to one of six sources.
A tub or a basin is a pitfall trap you did not mean to set: springtails fall in from a damp joint above and cannot climb the glazed wall back out. The drain is almost never the way in.
Springtails in a bathroom are not coming up the drain — they are living on one surface that never dries between showers. Finding that surface is the treatment, and this walks the six places it hides.
Springtails indoors are a moisture reading, not an infestation. Find the wet spot they came for, dry it out, and the numbers drop on their own.