I've got a whole shelf of treehouse dimple mugs.
I'd highly recommend Notch. Especially when they hold seasonal events. There's two locations. I'd recommend the Boston location as there's trillium very close by and others like Long Live and Vitamin Sea has pop up locations. Notch is Salem is a pita to get to from anywhere.
They also get good grades for their non alcoholic. It's been a while since I've had notch out of the can but draft is best. They do online delivery to most states
Fellow Masshole...love love love Notch, just never get there enough. As a lager guy, to me, they are the best brewery in the State. I know TreeHouse is always the top of any list, but there are a ton of breweries that make fantastic IPAs too, like as you mentioned, Trillium and Vitamin Sea and have to say in my town, Widowmaker cranks out great IPAs too. But Notch is constantly pumping out lager perfection and their one or two IPAs are not bad either.
Have you ever made the long haul up to Schilling in NH? They have moved to the top of my "best lager brewery in New England" list over Notch, after I visited there last year. Just world class stuff and all from a shockingly small brew space. Distribution to Mass is not as great as it used to be, as liquor stores reduced space for beers in favor of seltzers and canned cocktails after Covid. Can find a few locally and then there is a place in Boston at Haymarket, that usually has 4-6 different ones, so when we go to North End for dinner I will grab them. Otherwise a friend and I will every few months take the hour ride to just over the NH border to a craft beer store and load up on Schilling stuff we have not had before.
As for the best lager brewery in New England list, I guess it's really not much of a list

..Schilling, Notch, Jack Abby's and East Rock in my hometown of New Haven CT, are the only 4 lager centric ones I can think of. Oh, Sacred Profane in Maine too, owned by the girl, Brienne who was the head brewer at Notch for years. But they only make 2 lagers, Czech Pale, Czech Dark, though you can get a blend as a Czech Amber. Will say though, Tree House has really stepped up their lager game the last few years and Widowmaker in Braintree too, as started focusing on using traditional lager brewing methods for theirs.