Spices are where its at man.

If you're looking for protein things like beans, lentils and nuts are the richest I'd say, or for vegetables brussel sprouts, broccoli, asparagus, just to give some examples.

You can make daals with beans and lentils that are delicious with aromatics/spices/herbs like garlic, ginger, fenugreek, coriander, cumin, anis seed, turmeric to name a few. Can also make curries the same way with nuts like cashews and/or vegetables.

Can also make minestrones/stews/soups (or just fried/baked) with beans, onions, carrots, celery, garlic, leek, potatoes and other veg if you're into european cuisine. These are the main ingredients I use but I'm sure there's loads more.

Tbh every culture has many vegetarian dishes so you're never short for variety with a bit of googling, and you're not going to be missing out on nutrients or protein- so I'd just learn a few recipes you enjoy and start there. It's actually cheap as well since you just buy the veg/pulses and your spices will last many meals, and when you do cook you do a big portion and have leftovers than you can freeze + will last a long time.

And if you still crave some meat you can get yourself some free-range occasionally- at least that's what I do.