Afaik you can use your nsec as entropy and you will obtain a 24 word seed phrase right?
Discussion
the project of nostr:npub1fjqqy4a93z5zsjwsfxqhc2764kvykfdyttvldkkkdera8dr78vhsmmleku https://github.com/mleku/wordstr
this is the reference implementation of my proposal for a 256 bit exact word key encoding with 7 bits of check and 24 words
i have backed up my nsec on paper using it... you can at least use this tool to back it up even if the guardians of the nips don't approve the encoding
the algorithm is very simple... it turns your nsec into a giant 256 bit number, and then divides it over and over again by 2048, and the values that come out refer to a word in the BIP-39 word list and that's it... there is one extra 8 bits at the front, and i made it so the first (biggest, on the left) bit is always 1 so no matter what the first one returns something other than 0 because 0 is "abandon" and i don't like that word
yes you could use your nsec as entropy but it would be a seed and only like 192 of the bits are used