i know these are broadly used (seed phrases) but are any experts on these boards concerned about having to rely on more than btc core and using or possibility losing the ability to use them in the future (losing your keys?) due to not having access to the software to access (apps that implement BIP39)
is that idea i have unfounded?
BIP39 algorithm is open source (is known) and pretty straight forward so it is very easy to implement. This means there isn't a need for a special software written by some super expert programmer to be used. If you know basic programming you can write a tiny script that performs what's needed in BIP39 to convert your seed phrase to a private key.