Extracting the hard disk from a 15" Macbook Pro motherboard

This from a well known fixit website regarding the 2019 15" MBP w Touch Bar:

(it's not an HD proper, it's flash storage, by the way)

Technically the data is already hardware encrypted because a 2019 laptop uses the T2 security chip. However, if Filevault is not enabled, then it can allow someone to try to put the laptop into Target Disk Mode to access the data. If Filevault was enabled, then an admin user password would be required to mount the volume. Target Disk Mode typically can be accessed even if the system won't boot, but with these USB-C Macs Target Disk Mode is not quite as useful.

Destroying the T2 chip should be enough to prevent any access to the data since it would have the encryption key.

<< Although I am aware that the HD is soldered to the motherboard,

I have the tools and know how to disassemble it.  >>

I hope you have surface-mount de-soldering equipment, because it has lots of contacts, and they are far beyond the reach or an ordinary hobbyist soldering pencil.

How does knowing where the drive is located on the mainboard help in any way?

if you remove the mainboard, or even if you just remove the drive, the computer is then electronic waste, not a suitable donation item.

if you removed the display, and enterprising recipient MIGHT be able to use it, but ONLY for repair of that exact model. and only if they has very atypically high repair skills.

Was your drive encrypted?

If so, you are done.

Without the password, in the unlikely event the drive was read, it would be complete gibberish.

You're welcome.