My favorite thing to do is to make and freeze large batches of base proteins. I just made a bunch of pulled chicken in the crockpot on Sunday. It keeps for a long time even just frozen in a storage container or ziplock baggie as a single serving. Then when making dinner I just toss seasonings and toppings and have a wrap quickly ready to go. Add a side like a quick slaw or salad or even some chips and it's good to go.
Today I had some frozen leftover Christmas ham with a bunch or jerk seasoning, pickles, peppers, and some cabbage with a slaw on the side. Think it took 5 minutes to do up and didn't dirty anything I wasn't already dirtying while making dinner.
Tonight I'll probably do something with the chicken from the weekend. Could be flavored with taco seasoning, bbq, Cajun, Greek seasoning with hummus, Buffalo, teriyaki, any random Chinese sauce, some curry flavors, even left plain.
The other option is to make 2 to 3 times what you would for dinner and have leftovers for a couple of days. Not as ideal as you said you don't like eating the same thing over and over but personally I'm fine with it as long as something changes. Like if making tacos for dinner have a taco salad, taco dip, or make a soup by adding broth.
Soups are a good option too. Either canned or preferably homemade. They freeze really well and as long as you put it in the fridge the night before, thaws and heats up quickly in a microwave.
Pies/turnovers/pasty/calzone/empanada/whatever you want to call them are an option that takes more effort but can be used to have a frozen stash that's easy to grab after they are made and gives variety. One day of prep work can give lunches for a long time.
Good luck on your lunch adventures, it's hard to find new ideas that are not just make a wrap or salad or sandwich. And yes I realize that's basically what I wrote above.
Quesadillas.
On the higher effort end: whatever protein that has to be cooked plus onions, peppers, garlic, seasonings, and cheese. Then pan fried in whatever fat is left over from cooking the protein, adding butter if there isn't much fat like with chicken or turkey.
Medium effort: still pan fried but using canned chicken or any Mexican style meat that I've frozen.
Barely any effort just need to get food made: same as the medium effort but put together then tossed into the toaster oven until everything is melted.
Add salsa and chips and call it a meal. It may not be healthy but it's basically my go to when I don't want to put in the effort of cooking something as I always have everything on hand.