How is Facebook tracking me, and how do I make it stop?

I don't have a Facebook account, nor do any social media. My home network has a home built Debian router running AdGuard Home for DNS. I run Debian on my laptop with Firefox with uBlock Origin.

I'm a fairly privacy focused person.

Yet when I'm watching something on Ruku, or searching for something online while my spouse is scrolling through Facebook on her iPad, she gets relevant ads based on what I'm watching or searching for.

For example awhile back I was on a shark tank kick, as I worked through the seasons, she would get ads for products we were watching.

Just now I was searching for pet prescriptions and lab tests, within 15 minutes she got ads for both.

This is nuts!