Cheese is delicious. Many different cheeses are many different delicious. Unfortunately, many cheeses also produce many greenhouse gas. And only many female cows can give many milk for making many cheeses, but male calves are useless for making many cheeses, so many must be eaten.
Pardon my grammar escapade; I guess Grek and Thag were still spooking through my mind. Also, you can probably reduce the negative impact of cheese by buying it locally, from farm house production. But that's too expensive! 8-o So you need something to put on your bread while you're saving for the next delicious Oscypek (if you live in Poland) or Dorset Blue Vinny (if you live in Dorset) or Wurme (if you live in Mongolia) or Queso Asadero (if you live in Northern Mexico) or… Anyway, if you need something to put on your bread, I suggest the following:
If you want to surprise a Japanese person, one way is to tell them that you eat miso spread on bread. It is very unusual to use it in that way, but I think it is also very tasty to use it in that way. Mind, though, that miso is quite salty, so either spread it thinly or, even better, combine it with other ingredients in a miso sandwich.
$3–$8/500 g and you only need small quantities
I would expect to find large-industrially produced miso in (East) Asian shops all over Europe and North America. Look for plastic bags or tubs with yellow-white, brown-red or dark brown paste inside. A guy in a Japanese miso shop told me that such miso is usually produced in an accelerated (weeks instead of months) process and contains no live bacteria. In my experience it doesn't taste as good as traditionally produced miso, but it's still okay.
Those three to six different bags you'll find at the Asian shop are far from how diverse miso really is. In Japan there are many more kinds of industrially-but-traditionally produced miso and you can find local, hand-made miso everywhere, all with different flavours. If you're not in Japan, but another East or Southeast Asian country, you'll find similar products. And the Wikipedia page linked above tells me that people all over the world are adapting the process to their local grains and pulses. So, while miso doesn't reach cheese in variety, it certainly offers more than enough to explore.
Make it yourself
Making miso is not too difficult, but takes a long time and requires things like a cellar and koji. I've never done it, although I would really like to experiment. If you're interested, you'll find instructions in Sandor Katz's Wild Fermentation and on the web.
The Japanese use miso for miso soup and so can you! Just make stock from kombu and dried shiitake (easier than any other kind of stock!), cook sliced leeks and potato cubes in it, take off the fire, stir in miso and serve in bowls. Search the web for more detailed instructions and recipes for many more Japanese dishes with miso.
Wild Fermentation recommends making a dressing from miso and tahini. See there for the recipe or search the web. If you've got too much of some cheap miso, you could use it instead of salt in many dishes, adding it towards the end of the cooking. In Japan they have miso bread, which is not like normal bread, but I expect that miso works well in normal bread recipes, too. Just don't use too expensive kinds, because the baking would destroy much of the flavour.
I have a bunch of suggestions, but it takes time to write them all up. Next might be Marmite, but before that, I have to write about the miso sandwich.