If your diet mainly relies on wheat and animal products and other things stockpilers are swiping from the stores, hunting down needed non perishables can get really hard.
Based on our experience, here are some things that may be worth considering as substitutes.
(aimed at building up some supplies)

GRAINS:

Maize
• flour (preferably treated with limestone)
• samolina for e.g. Polenta
• whole grains, canned/frozen
• popcorn
• pre-made tortillas etc.

Rye
• flour
• whole grains (can be cooked like rice or soaked and baked etc.)
• pumpernickel and similar packaged breads (often with sunflower seeds)

Rice
most conventional kinds were gone, but
• brown rice was still unpopular in our area
• rice flour
• rice noodles

Oats
• muesli with raisins still unpopular
• porridge (some mixes contain powdered milk)
• granola

Buckwheat
• flour

Spelt
basically it's wheat, just not as "fluffy" when baked

Seitan
(wheat protein)

Make sure to complement those with legumes as well as vegetables like carrots and squash to ensure balanced intake of amino acids, if animal products will be stripped from your diet.

Animal Products:

Eggs
• preboiled eggs are better preservable
• buy eggs and boil them to store them longer, look up expiration dates online

meat products
• jerky
• some salamis are affordable
• canned products/soups

fish
• canned tuna
• herring products

LEGUMES

• peanuts
• lentils were mostly available
• precooked beans, peas and chickpeas, usually canned
• dry soy products
• flour made from legumes
• noodles made from legumes

SEEDS and NUTS:

• sunflower seeds
• poppy
• sesame
• almonds
• hazelnuts
• walnuts
• cashews
(good for essential oils and electrolytes)

OTHER

(vegetables that can be stored well)
• precooked or raw pickled vegetables in jars/cans
• squash
• sweet potatoes
• cabbage
• onions (though need to be checked)

• dried or frozen berries
• dried banana, mango, apples, apricots, dates, figs, plums
• jams/spreads
• apples
• applesauce
• canned (or other) tomato pulp
• leafy greens as available (germany has some common staples in jars, not sure about other countries)

Try to get differently coloured veggies and fruits, secondary plant products are as important for health as vitamins.
Canned products often contain added sugar and salt.
Dried products can increase your uric acid level.
Please watch out if you have related health conditions.

This list is in no way complete and depending on hoarders' choices not reliable.
Hoping this may help some of y'all anyways and for y'all to stay healthy and safe during the crisis.

If anyone knows better resources on this kind of thing please share in replies!

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