Description:
Promtail instances with the journal source enabled are no longer sending journal entries to Loki. This issue appears to have first surfaced around the time the promtail package was updated to version 2.8.0.

The below warning is observed in the journal for the promtail service
`WARNING!!! Journal target was configured but support for reading the systemd journal is not compiled into this build of promtail!`

The Loki 2.8.0 upgrade guide makes note of the introduction of a new build tag called `promtail_journal_enabled` that must be passed to include journal support in the promtail binary.
https://github.com/grafana/loki/blob/release-2.8.x/docs/sources/upgrading/_index.md#the-go-build-tag-promtail_journal_enabled-was-introduced

To restore the behaviour prior to Promtail 2.8.0, it would now be necessary to set this build option.

Related issue on GitHub about the upstream binaries themselves missing the new build option. Grafana are planning to add back journal support with their next official binary release of Promtail version 2.8.1 coming soon.
https://github.com/grafana/loki/issues/9060

Additional info:
* promtail 2.8.0-1
* promtail.yaml config on sending machines includes

```yml
scrape_configs:
- job_name: journal
journal:
json: true
labels:
job: journal
```

Steps to reproduce:

* Install promtail
* In promtail.yaml, configure a Loki target to push logs to (clients: - uri:) and the journal source - https://grafana.com/docs/loki/latest/clients/promtail/configuration/#journal
* Start promtail service
* The journal stream is never received by target Loki instance and messages are displayed in journal about the promtail build lacking journal support as above