You don't have to try all combinations. You can start with the most probable ones first.

For example, you can start by only assuming you made a single error. Private keys are usually encoded in base58 afaik, so every letter could have been any of these 58 characters. Generally, you could even go farther and check for "common typos" first. However, since base58 explicitly excludes letters which may be mistaken for other letters, I don't think that makes sense. There shouldn't be any common typos from reading or transcribing a private key encoded in base58.

So in your case, I would first try to change a single letter. If that doesn't work, try combinations of two letters etc.

Good luck.

Why are you storing the private key instead of the seedphrase? QR is an extra. Seedphrase is what's important.

If I'm reading this right, 51 characters should take around 18 quadrillion-zillion years

the phrase can only match a word list where all words were intentionally unique enough that it's hard to do this.

Yeah mate, you can chalk that one off as a loss, thats why we have seed phrases now, because too many people stuff up private keys. Unfortunately, those funds are now a burn wallet and you've removed a few sats from ever circulating

Forget that account. That key is only to one address. Restore the whole wallet somewhere else with seedprase.

1GsAFeF3S5Bt1JU6CjjAzNtfgnzoXkyUnh

the address