ESP32 Best practices for filesystem on external Flash

[artificiel]

hello! i've got a fairly satisfying experience running a sampler with up to 4 asynchronous WAV generators in a mixer outputting to I2S. the audio files are downloaded as needed from a server with HTTPClient and cached/saved in SPIFFS for repeated use. SPIFFS is tight with uncompressed audio and i'd like to move the audio files on an external SPI Flash chip.

there seems to be many paths to achieve that goal as well as many bits of info (such as SPIFFS being deprecated) and i was wondering what are the currently recommenced "best practices" in terms of handling a filesystem on external Flash that works transparently and efficiently with ESP8266Audio.

i guess i'm looking for something like PlayWAVFromFSinSPIFlash?

my current understanding would be to build on Adafruit's SPIFlash (very well documented in Renzo Mischianti's post), and tweak components of ESP8266Audio as needed (probably write an AudioFileSourceFATFlash), but before embarking on that i would really appreciate any pointers re: specificities of ESP8266Audio -- perhaps there are better suited components available, or maybe it already exists and i did just not manage to recognize it?