Prenote

Congrats on trying out veganism!

First off, based on your message, I think you might have a couple misunderstandings about veganism. Understand that veganism isn't a diet nor is it inherently healthy. You can be vegan and eat processed food and imitation products all day long. Veganism is primarily an ethical stance - choosing not to partake in the industrial scale abuse and torture of our animal friends.

I hate to say something that goes against my own beliefs, but I don't think it really makes sense to go fully vegan just for health reasons. Yes, virtually all nutritionists would say that people need to cut down and significantly reduce the amount of meat and animal products people eat, but for purely health reasons there aren't many reasons to go down to absolutely 0. Plus, although there are plenty of benefits to outweigh the negatives, it is important to recognize that vegans can have a slightly harder time getting some nutrients, like vitamin D, iron, zinc, omega 3 fatty acids (most people struggle with these nutrients anyway, it's just that vegans struggle a little more). And uniquely, there is virtually no vegan source of B12, so you need to take a supplement, or eat fortified foods.

I'm saying this because people who go vegan only for health reasons almost always quit eventually. Do it for the animals, but also enjoy the health benefits that come along naturally.

Don't make these mistakes

Going vegan, especially suddenly, can take a toll on your body, just as making any sudden dietary change can.

• Make sure you are eating enough. A lot of vegan food isn't as dense as animal products, usually because it contains a lot more water. The actual "volume" of food that you eat should increase quite a bit. Although I'm normally against it, I actually recommend calorie counting for a bit when you first go vegan (but do understand the dangers of calorie counting long term).
• Understands symptoms of suddenly eating a lot of fiber: One of the healthiest aspects of veganism is the high intake of fiber, which is fantastic for your digestive system. However, most people eat way too little fiber, and the sudden change from little fiber to lots of fiber can actually be a bit uncomfortable: bloating, stomach pain, diarrhea. Long term healthy, but maybe short term take it slow.
• Eat satiating foods: Vegetables and fruits are great for your health, but you have to eat foods that provide long term energy and make you feel full. If you are feeling hungry all the time, that's not good. The overarching categories here are grains (preferably whole), legumes (beans, lentils, tofu, fake meat), nuts, seeds.
• Get your vitamins checked 3-6 months after going vegan: I just think this is too important after any dietary change.

Onto your actual question

The main breakfasts I eat are:

• Granola or cereal and plant milk
• Tofu scramble (can meal prep this easily) and toast, sometimes impossible breakfast sausage. To make good tofu scramble you need some unconventional ingredients you might not find at a grocery store, like black salt (kala namak)
• Beans and toast
• Leftovers from last night's dinner
• Skip breakfast (or just eat a small fruit) and instead have a big lunch

I will occasionally have toast with peanut butter and banana on it, but that's so calorie dense, I only eat it on days I know I'll be doing a lot of physical activities.

This is actually a great breakfast. I understand your concern about it being calorie dense, but recognize that this is very satiating, and will keep you full and energized for a long time.

Also, don't be afraid to eat some vegan imitation products. I promise they're not nearly as bad as people demonize them to be, just don't eat them all the time. I love impossible brand breakfast sausage, bratwurst, burgers, and chicken nuggets. In modern day, you can be vegan and still indulge in some tasty foods occasionally.

If you like oatmeal, try overnight oats. Add some water, touch of maple syrup, your favorite fruit, dash of salt, and put it in the fridge. You can make a week's worth at a time, and try different recipes to see what you like. I went through a phase where I tried all sorts of recipes, not all vegan.

You can add other grains, too. Barley worked surprisingly well, but chia seeds had that gelatinous texture I don't care for. Pumpkin seeds, cashew pieces, and poppy seeds were all good. You can also stir in peanut butter, nutella, sunbutter, or cookiebutter if you want to make it more of a treat.

If you’re just desk jockeying for 10 hours, I’d say skip the breakfast entirely. A nice iced coffee (black or splash of oatmilk) goes a long way towards curbing hunger.

If you absolutely MUST eat in the morning, a smoothie is nice and cold, quick to make, and can be as high/low in calories as you desire. I make mine with a banana, frozen strawberries, protein powder, peanut butter powder, and soy milk (~300kcal, 30g protein) but I only have one on days I go to the gym (4 days a week)

Scrambled tofu with spinach, salsa and toast.

I've gotten into polenta recently. I cook it up ahead of time and put it in a sealed dish in the fridge. When it cools and sets up, it's easy to slice into sections and eat as finger food. I can eat it plain, with hot sauce or sometimes I'll saute up vegetables (peppers, onions, zucchini, whatever) and add them to the polenta before it cools. The particularly cool thing is that I can eat it hot or cold. Once it's set up, it toasts up nicely too.

I go for musli on soy milk most of the days for a fast set of protein and fiber, you can go with a very low sugar level with that, and there are so lo-carb veriants usually. You can also make your own soy milk if you want to set it to your taste.

If youre fond of it you can make sceabled tofu (a'la egg), some 'black salt' will give it a familiar taste. Otherwise some veggie/seed paste and a slice of tofu work great for me. I stopped bothering with the highly processed vegan meet-like products, they cost a ton and you can make your own pastes easily.

If you want to return to being a cereal person, try a minimally processed no sugar cereal such as Uncle Sam, with a no sugar plant milk such as West Life soymilk.

Right on! Maybe look into some of the fake eggs/omelettes that are available these days, so you can re-create something that you know you like. I had a vegan friend who really liked them. I don't know that toast with peanut butter and banana is more calorie dense than an egg and bacon burrito. A smoothie might be nice in that hot Texas heat

https://vegetarianism.stackexchange.com/questions/2571/what-can-i-make-for-breakfast-thats-vegan-and-requires-very-little-time-and-eff