For now you have to replace a package with another one. This will not alter any behavior of the itx-3588j but adds a service which will fix bluetooth at boottime.
itx-3588j-post-install. This packages sets a needed parameter to work around a standby issue. Fear not we will fix this again.sudo pacman -R itx-3588j-post-install
r58x-post-install. This package provides the same fix for standby as mentioned above and includes the service bluetooth-mekotronics.sudo pacman -S r58x-post-install
The Bluetooth adapter is not connected to /dev/ttyS9 (as it is with other RK3588 single-board computers), but to /dev/ttyS6.
/usr/bin/bluetooth-fix.sudo nano /usr/bin/bluetooth-fix
#! /bin/bash
/usr/sbin/rfkill block 0
/usr/sbin/rfkill block bluetooth
/bin/sleep 2
/usr/sbin/rfkill unblock 0
/usr/sbin/rfkill unblock bluetooth
# FIXME Delay
/bin/sleep 1
brcm_patchram_plus --enable_hci --no2bytes --use_baudrate_for_download --tosleep 200000 --baudrate 1500000 --patchram /lib/firmware/ap6275p/BCM4362A2.hcd /dev/ttyS9
/dev/ttyS6.brcm_patchram_plus --enable_hci --no2bytes --use_baudrate_for_download --tosleep 200000 --baudrate 1500000 --patchram /lib/firmware/ap6275p/BCM4362A2.hcd /dev/ttyS6
bluetooth-mekotronics.sudo systemctl --now enable bluetooth-mekotronics
That's it! Bluetooth should work fine now.