I'm GF but not allergic (so you won't be wanting to hear about the salmon, tuna or prawns) - but the combination of flavours might help;
Carbs - long grained rice, sushi rice, GF pasta, glass noodles, pure buckwheat soba noodles, boiled potatoes, quinoa
Protein + seasonings - chicken breast or thighs, beef, pork, halloumi, feta, boiled egg - garlic & lemon marinade; garlic, chilli, lime and coriander; yoghurt & curry spices; tahini, lemon juice and a little water; tamari, sake and mirin; GF and seafood free (it exists) gochujang, GF miso of various types; five spice powder; thyme and mustard, pesto, peanut sauce (add chilli, onion, garlic, chicken stock, coriander and spring onions)
Cooked veg - broccoli, butternut squash, edamame beans, corn, fresh plums cooked down with some GF plum sauce, tamari and sake (add some rice vinegar if it's too sweet), green beans.
All of the salad veg. Lots of herbs.
Tinned bean salad in vinaigrette.
Pickles - beetroot, dill, olives, artichokes, pickled garlic.
Fruit - grapes with cheese, watermelon with feta or halloumi, plums, peaches, pineapple with pork, fruit salad in a separate compartment with yoghurt, berries.
Snacky things - brazil nuts, walnuts, dates, homemade popcorn (sea salt and a drizzle of syrup).
You could make GF nuggets, spicy or otherwise, buy GF mini Kyivs, have mini brie and grapes.
There are so many variations, you needn't have exactly the same thing twice - and none of that requires a microwave (and looking at most workplace microwaves, you probably wouldn't want to be anywhere near them with a fish allergy).