The two big supermarkets I normally use are both going through major refits that has resulted in reduced stock - but even allowing for that there are some things that are missing from pre-COVID and pre-Brexit days. Some are European imports that have vanished or jumped in price, others are down to interruptions in manufacturing (may or may not come back). Big jars of Marmite last seen in June 2020! But now the pubs are back in business and brewing (and glass bottle production) restarted I live in hope!