Can you place a Dripstone on a hopper?

Update Suppression.

This is a very tricky mechanic, detailing which could take an entire book. Or an over 40-minute video:

In brief though - update suppression allows you to break or place any block without affecting any* neighboring blocks. In case of dripstone, you'd place it on any regular block it can be placed on, then remove that block while suppressing updates from removing it (and in effect obtain pointed dripstone floating in midair), and then place a hopper while suppressing updates from placing it.

Since both building the update suppressor takes a bunch of work and resources, and then operating it requires drawing the update-suppression line to every block you want to suppress while observing all the restrictions associated with directionality of the operation, and possibly resetting the update suppressor manually after every operation if you didn't go through even more work to build a self-resetting model, it's hardly worth the effort in this case, although there are applications where it can provide massive benefits.

^{*) not quite "any" as it's very directional; sometimes it will require a very specific build order. Sometimes the geometry restrictions will make certain operations impossible to perform. Or some blocks will be affected in surprising ways (like wither skeleton skulls getting bleached into regular skeleton skulls.) And there's a considerable risk of crashing the server.}