On PureOS 8.0, kernel 4.18.0-2, reading/writing firmware using flashrom (included 0.9.9-r1954, as well as v1.0 and upstream master compiled from source) in conjunction with a CH341a USB flash programmer fails, with a LIBUSB_TRANSFER_TIMED_OUT error. Running verbose mode shows data is being read/written, just eventually times out. No error under any other Debian or Ubuntu based distros tested (GalliumOS 3.0, Mint 19.1, Ubuntu 18.10, Debian 9.7.0). PureOS's libusb-1.0.0 package was installed under other distros to test, and had no issues, so points to a kernel/OS config issue vs a libusb issue.
flashrom does not even display its version number via flashrom —version - it complains about being unknown on PureOS after being updated from 0.99 => 1.0.
$ flashrom flashrom unknown on Linux 4.19.0-2-amd64 (x86_64) flashrom is free software, get the source code at https://flashrom.org
additional note: this doesn't appear to be a kernel issue, as I installed the Liquorix kernel and had the same result there - so must be one of the underlying packages libusb depends on