Bachelors Beanfeast is the first “vegan” thing that I can remember eating, must have been about 1980 (though I was far from vegan then) I can remember being surprised how tasty and filling it was.
I never use those yeast flakes because I spent so long working in a microbiology lab and the ever present smell of autoclaving malt/yeast extract agar together with that of all the crap that had accumulated in the bottom of the autoclave has put me off for life. Quite fine with marmite (Meridian version)though.
I started buying occasional jars of B12 tablets a few years ago after thirty years or so of veganism. If you eat enough fortified foods you will be fine but sometimes I go months with no soya milk/marmite. And B12 supplements are simply a fermentation product of bacteria – nothing wrong with that