i only plan to carefully write the seed on a piece of paper (or better engrave
the seed on steel) before leaving. That being said, i noticed that Electrum
said that BIP39 seed might no longer be supported in the future, and, one the other hand, if i
create an Electrum seed it might not be accepted on other devices. Since my
aim is obviously to have access to my BTC later, i'm puzzled. How can i predidict the
standards in ten years?
Perhaps saving the master private key as a QR code might be a better idea...
One of the importance of seed phrase is the ease to back one’s wallets without having to store the master private key or any key at all. I get where you’re concerned about, like electrum not been in existence again, currently there is a BlueWallet that is said to support the custom seed phrase from electrum wallet.
But aside that should they stop to build/develop the wallet again, another developer could easily build it up since its source codes are open.
But also if at a time there is no wallet that supports the seed phrase, you can still generate the master private key from the seed phrase using tools because the method it uses to generate its seed is not that different from the Bip39 seed phrase. So there is nothing to worry about