Depends on the mood you are in. Technically life alive is a chain but the lowell one has completely different vibes from the ones you may find in the greater boston area and it feels like a local vegetarian restaurant,

Sizzling kitchen is also very good, sizzling platers are a real fun experience.

If you are willing to park downtown to pick it up, espressos pizza is (in my families opinion) the best pizza in Lowell. But if you prefer a thin crust tre monte may be more your style.

Up in Pawtucketville there is the eggrole cafe (although maybe still under renovations this week, unsure) and an Egyptian food truck that you can tell by the bright green.

If you want a more hipster vibe, coffee and cotton in mill #5 is a nice little cafe. And you can head to the soda fountain down the hall for a nice float made with vegan ice cream (I just had their homemade moxie with vanilla ice cream today)

If you want breakfast, I am partial to the owl diner, or if you are willing to cross the border to the north into Dracut (where I grew up unfortunately) you can find Bobolas diner which I grew up on. And if you are in the mood for something truly special. Go two towns up (I know, pushing the whole “local” clause but still its worth the travel) just over the NH border to the broken yolk cafe. Almost always has a wait because it has some of the best breakfast foods you will find.

There are also more restaurants I haven’t been to than I have so I recommend try restaurants you haven’t yet. It may be fun.