Most definitely, yes. Thunderbolts is pretty much a Black Widow sequel, as Yelena is the main character, and also Red Guardian and Taskmaster get introduced in Black Widow. I would also recommend watching Hawkeye if you haven't, as that explores more of Yelena.

Same thing with TFaTWS. Expands upon Bucky's story and also John Walker is introduced in that show.

I'm not a fan of any of those projects apart from Hawkeye lol, but I would say they are necessary to understand what's going on in Thunderbolts*.

The Falcon and the Winter Soldier is something you need to watch

Same with Black Widow

Ant-Man and the Wasp I guess you can watch to understand who Ghost is

Other than that I don’t think there is any other project you need to watch for this movie

Black Widow and FALWS is 100% needed, you can watch Hawkeye if you care about Val and Yelena relationship.

The Black Widow movie introduces Yelena Belova, Taskmaster, and Red Guardian, and also features Valentina Allegra de Fontaine. The Falcon and The Winter Soldier introduces John Walker/U.S. Agent, has Bucky Barnes in there and shows their dynamic, and also has introduces Allegra de Fontaine. So yeah, if you're doing "prep" for this movie, those would be the two I'd recommend.