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There’s millions of hardware wallets in existence right now generating 24 word seed phrases offline. Surely somewhere in the world there must be two or more devices that have generated the same seed phrase?
Bonus question: Does the 12th and 24th words being a checksum (so not randomly chosen out of 2048) make it more or less to be universally unique, or what is this checksum's importance security-wise?
Ledger phrases are generated following BIP39 standard
Its basically a library of 2048 unique words sorted in alfabetic order.
Therefore generating phrase by pickin 24 words at random gives you 2048^24 = 2^264 combinations,a number so astronomical there is no realistic chance of two wallets/people randomly ending up with the same phrase.
However because (as you noted) 12'th and 24'th words are checksum, the number of variations drops from 2^264 => 2^256 ,yet that is still more than a number of atoms in the observable Universe.
The number 2^256 is likely something you have already seen A LOT of time, because it's used in EVM constantly.
Reason for that is that Ethereum private key has 256bits => 2^256 possible combinations too. In fact, your recovery phrase is simply your private key writen in a different (more readable ) format.
