What's the easiest way to discover and tests variations of a seed phrase with an invalid checksum? Are there any simple tools out there to help with this?
Discussion
Could use tails os offline with electrum, or even this website offline https://iancoleman.io/bip39/
nostr:npub17tyke9lkgxd98ruyeul6wt3pj3s9uxzgp9hxu5tsenjmweue6sqq4y3mgl has a way to let you do it…putting first 11 or 23 words, then select remaining random bits and valid check sums supplied for that bit set. I can show you screenshots in a few mins if you want.
I think the issue is with one of the prior words though. The checksum is a word with not a lot of similar options.
The checksum is the last 4 bits of the first 23.5 words. You out in 23 words and then manually put in 0000, 0001, 0010, etc for all 16 combinations
Turns out it’s just 3 bits of extra randomness, so only 8 combinations to try.
Are you working on a 12 or 24 word seed? 
This nostr:npub17tyke9lkgxd98ruyeul6wt3pj3s9uxzgp9hxu5tsenjmweue6sqq4y3mgl feature lets you use the words themselves as entropy source. A big bottle of 1024 double sided seed word orange pills. 