No small drain snake?
(Some newer sink drains / stoppers won’t let you get one in.)
Find tools, take drain plumbing apart.
Gotta be careful with old metal drain plumbing, though. “Draino” a few times, or even corrosion over time can eat it away from the inside. I’ve broken such easily with my bare hands.
Plumbing supplies were near the top of our prep list in late Jan/early Feb.
Especially replacement things for the toilet and fixit stuff for any leaks we might have.
Probably not too late to get that stuff but you might have to order it from a bigbox and have it delivered. Or venture to your local ace or order from ace.
There are LOTS of fixit videos on utube.
It’s the problem sink. Two plumbers want to drill through the foundation. I’m not buying that. They refuse to look where I tell them. There’s a T instead of a Y.