What can be done with accidentaly oversalted beef?

Oversalting is best dealt with by serious dilution.

I'd make a large, not very meaty dish from it, with lots of vegetables, cooked for a while. Fry onions and other veg, add liquid, and stir in the cooked beef. But soaking the meat should help as well. Either soak in plain water and discard the water, or soak in something you might add to the sauce (wine, beer, diluted citrus juice... ). I'd also cut it small before soaking/cooking. Most of the salt will be on the surface but you want to expose add much as possible of the meat to the liquid. Soaking should be done in the fridge, for a few hours.

You could go for a tomato-based sauce, a curry using coconut milk, or a sticky orange and chilli sauce, so long as the ratio of beef to everything else (and beef to initial liquid) is small. The initial liquid shouldn't bring any more salt with it, which rules out most cmmercial stock preparations, and possbile home-made stock. These are just ideas, many beef in sauce dishes would adapt. I wouldn't add more meat, but many people would.

Make a soup out of it! Dice the meat up, sweat some aromatics (onion, celery, etc.) in a pot, put in 1-2 liters of water, add the meat and let it come to a boil. Then, bring the heat down to a simmer and taste it. If it's still too salty, you can add more water and/or adjust more seasonings to balance it out with the other flavors. If it's still too salty for your tastes, cook something starchy like rice, pasta or potatoes and then serve a ladle of soup on top, like a sauce.

Use raw potato. If the meat is already BBqued put in between layers of raw potato slices. Then reheat it [meat] by boiling it with whole potato, then for a short while put on preheated pan.

If you want to remake it into some other dish add celery bulb in cut in quarters. It will work same as potatoes but will also add some sweetness that will counter saltines. After preparing the meal throw out the celery.

It sounds like you're half way done with making beef jerky. You just need to dry it out now. If you don't have a food dehydrator, you can dry it in a very low oven, or use Alton Brown's method with box fans

If it was just salted, it'd be cecina, but you might want to look for recipes using it for ideas how to use it. (eg, cooked into scrambled eggs or a hash)

There's a Chinese dish ?????? - I'm not sure of a good English translation) with thin strips of salted pork (similar to bacon, but saltier) fried with chili peppers. The meat is too salty to eat on its own, but when sliced thinly and used in moderation with the peppers it makes a nice dish.

It's not a perfect solution, since the pork used is quite fatty and you have lean cuts of beef, and it is tricky to slice already-sliced meat, but the basic principle (fry with a vegetable) should work - even if the meat is inedible, it should give a nice flavour to the vegetable.