Need to remove caulk/sealant

Replacing gutters & sections of wood behind them. My in=laws themselves added this extension back in 1975. The sealant or caulk they used, frankly, is kicking my butt. He passed away from Dementia 8 years ago & at 82, she doesn't remember what they used

It's like pure rubber. Every tool I've tried literally just bounces off. Scraper/putty knife, utility knife, razor knife, chisel, you name it I've tried it. Nothing makes much difference.

It won't peel off either. It stretches probably 500% before one tiny little piece 1/20 the size of the original snaps off.

I'm now resorting to chemical solvents to remove this gunk from the metal flashing/drip rail along the edge of the roof that the new wood fits behind. Just not sure what will work most effectively.

I don't want to blow a bunch of money trying out different products. Any suggestions? I don't use a lot of chemicals. The strongest one I know of is acetone.

Thanks

 

Post a picture.
I use an oscillating saw to remove caulking.
No even sure why they used caulking on gutters or a fashia.
What's the end plan?
Are you going to end up with this house?