What should I do with my old MacBook Pro?

You could use it for

• running old 32-bit games that won't run on Catalina and later
• importing digital video, over Firewire, from old MiniDV and Digital8 camcorders
• running an Intel-based distribution of Linux
• a spare computer for a school-aged child to run a word processor on (I believe you can still get old, unsupported versions of LibreOffice that run on High Sierra)

or give it t someone who you know has such a use for it.

Otherwise, the day may have come to retire it or recycle it.

Take it to your nearest Apple Store and they’ll recycle it properly for you.

Before you do that make sure you read this article first: What to do before you recycle your old Apple device