Android firefox and flash wear

I don't really count integrity as security but most do and I am
subscribed to this list so...

Before quantum it was fiddly but you could set the download directory
but now it appears to no longer work.

Firefox apparently aims to be similar on all platforms so why is the
download directory menu option missing.

The problem which is more important on Android as I doubt space is
reserved on phones for wear leveling is that if the filesystem is
approaching full then the usual guarantee of more recently 10,000 flash
writes could cause issues in irreplaceable long term phone memory.

So if a user makes large downloads frequently such as weekly system
updates, surely it makes more sense to allow them to wear out the often
larger and replaceable SD even if standard SD (contrary to what many
believe) has next to no wear leveling features?