This definitely reads like one of my KSP exploits...

Alternatively you do like the Parker Solar Probe and do 7 Venus flybys, bleeding off a little speed each time with an inverse gravity assist.

Not an expert, but I've read it's easiest to use jupiter to bleed off enough velocity to fall into our sun.

the issue is not counteracting gravity, the issue is decelerating enough to hit the sun

Why would an orbit decay without something to slow the spacecraft down like an atmosphere? The problem is that any object we launch from earth has a lot of orbital velocity, which makes it almost impossible to hit the sun directly, you would have to use a lot of complex gravity assists from the inner planets to take away enough momentum. Using gravity assists to accelerate outwards is much easier

I remember watching a video about that. The gist is that you have to leave earth orbit or something idk.

You're starting with the speed of the earth

To escape a body of mass you need to have enogh velocity (kinetic energy) to overcome the gravitational pull of that body. You can imagine it like a ball sitting in a bowl. With little velocity it will just roll back and forth but if it's fast enough it can roll out of the bowl and escape it's influence.

That critical speed is called "escape velocity" and it depends on mass and distance from a body. The escape velocity of earth (from the surface) is about 11.2 km/s and the sun's escape velocity (from earth orbit) is about 42.1 km/s. Earth orbits around the sun at about 29.8 km/s. If you launch in the direction of Earth's orbit, you will orbit the sun already at about 41 km/s, so you "only" need 1.1 km/s more to escape the sun, too.

If you tried to reach the sun, you could launch in the opposite direction leaving you orbiting the sun at about 18.6 km/s. Since there is almost nothing in space you won't slow down from friction and the orbit won't decay. Instead you'd have to accelerate opposite the direction you're traveling. Now, calculating exactly how much you'd need to decelerate isn't trivial since you don't want a stable orbit but an elliptical orbit that just touches the sun at the closest point (perihel). I don't know how much deceleration that takes, but it's propable that it's easier than accelerating by 1.1 km/s to escape the sun.

When the sun dies it will take the earth with it iirc so if you can wait until then you're good

The issue is that you're starting from earth, and the earth already has a lot of momentum that keeps it from falling into the sun. To get an object from here to the sun you would need to counter the majority of that momentum it already has.

Newton's third law of motion clearly says that this will take exactly 0 ∆V.

If we're going for a bigger target, let's go all out and aim for Stephenson 2-18. Go big or go home!

Just launch lots of tiny bits of processed earth at them super fast. More propellant efficient and you don't have to worry that they might have packed a parachute.

You'd still be moving some 30km/s around the sun, and need to decelerate from that speed.

More than Elon had, apparently.

The only way to be sure is to try both ways in Kerbal Space Program.