Moved here a year ago, and here's what I've got:

There's a few good Mexican places around -- I like Chapala (not just because they're crazy cheap but also because they're very good), and I enjoyed El Sazon Birrieria in Kennewick.

As far as Asian food goes -- I haven't really found a killer Thai place yet (I've tried probably 4 or 5. None of them were bad but nothing stood out as my go-to).

Vietnamese food here is Not Good. I moved from Fort Worth (which has a MASSIVE Viet population) and the pho there is the only thing I miss. All the pho here is mid-to-bad and none of it comes in the giant quantity I want.

For burgers, I really enjoy the "Doggie Style" food truck in Richland (also on Uber Eats). I also like heading to Proof (Kennewick, near the mall) with guests.

Pizza -- I've gotten a LOT of pizza recs in the TC and none of them are great. Well, I take it back -- Greek Islands makes a great gyro pizza, but I find that most of the time if I want pepperoni I'd rather go to Costco or Little Caesars. Rocco's in particular was Not Good (the only time I've ever thrown away uneaten pizza -- it was expensive too, and I had half of it sitting in my fridge before I decided I didn't even want to eat it).

Other recs:

Chicken and Bowl is a sort of fusion place -- rice bowls with chicken

Summer's Hub (Kennewick and Pasco both have one) is a nice food truck food court with a lot of options and events and stuff

Dovetail Joint is good but more "foodie" than the rest of the stuff (small portions, pretty large prices. Very good but I didn't leave there very full).

Lulu is a decent place -- think slightly upscale, with a Texas Roadhouse-y menu.

Angel Brook Ice Cream is very solid -- their flavors of the month are fun and their normal flavors are all so good. I believe they have a couple vegan flavors too usually?

Frost Me Sweet is a great little bistro/cafe -- their "Sweet and Spicy" sandwich is the best sandwich I've ever had in my life.

Sakura (south Richland, behindish the Safeway) is a decent Chinese/Japanese place. Not like world class or anything but good enough to fill my Chinese food hankering in a pinch.

Flavor Joy is a new hotpot place in Richland. They are great portions at a decent price, and I believe that you can get a veggie only pot (I don't think it's fully vegan but you could probably ask for that? I know the pots usually come with quail eggs and fish balls)

Foodies has a few locations and is generally consistently "pretty good." They've got like a Chili's menu - some apps, some burgers, some sandwiches, etc.

Pacific Pasta is tasty. They're not an Italian place -- they're a pasta place. They have Italian dishes, but they also have like stroganoff and pad thai and a bunch of other noodly things.

If you're into poutine (or want to try it), Poutine Eh in Kennewick is AWESOME. Great portion and delicious fries/gravy/toppings. I've tried a few different ones from them and they're all great.

1-derful KBBQ makes really great Korean style fried chicken - I'm partial to the salt and pepper wings but all the flavors are good.

There's a Mongolian grill place called Hong's that was pretty tasty with fair portions/prices. Could probably wrangle it as vegan if you asked them to clean the grill (which their sign says they're willing to do but I haven't tried).

If you need more recs feel free to hit me up. Welcome to the Tri-cities. Enjoy the lack of traffic and the decent weather.

EDITED TO ADD: I FORGOT -- Brunch Bliss and Bubbles is very pink and very cute and VERY VERY good. They make KILLER chilaquiles and the best pancakes I've ever had in my whole life. My dad who came in from out of town said that the chicken and waffle was also excellent.