There will be more like that, but we need to get better at identifying them. Just like with exoplanets.
Also, it seems like the space base weapons treaty is being ignored now (https://spacenews.com/russia-vetoes-u-n-resolution-on-nuclea..., https://www.npr.org/2024/05/30/nx-s1-4975741/what-to-know-ru...). I wonder if there is an opportunity to do some science with space-based lasers and spectroscopy. The energy would be small, but then again we can learn a lot just from the off-gassing created by the sun’s photons as well.
I doubt we're even near "impactor" capability, tbh. I think our best bet might be "catch up with something in the Oort somewhere around 2070, if we see something coming a decade ahead of time".
I actually think if the object was on the right trajectory and we had enough time, that you could pretty much park an impactor in its path. You could probably do a lot of science based on the spectra of the resulting cloud.
I agree that gently landing and return a sample with that much delta V is out of our reach at this point. Maybe with enough shielding, you could park a second sample return vehicle in the path of debris.
Project Lyra develops concepts for reaching interstellar objects such as 1I / 'Oumuamua and 2I / Borisov with a spacecraft, based on near-term technologies. [0]
Several technology options are outlined, ranging from a close solar Oberth Maneuver using chemical propulsion, and the more advanced options of solar and laser sails. [1]
It solves the disposal problem neatly, since the probe and reactor are both leaving the solar system forever afterwards.