PureOS itself does not support bluetooth because there is no completely free firmware for it.
Because PureOS 10 byzantium is based on Debian bullseye, you can download the relevant non-free pacakges from there if you want:
https://packages.debian.org/bullseye/all/bluez-firmware/download
https://packages.debian.org/bullseye/all/firmware-atheros/download
Then you can use a GUI or sudo dpkg -i packageName.deb to install them.
Finally, a reboot might be necessary to get bluetooth working.