"I installed splunkforwarder-8.2.9 on Oracle Linux 7.4 and added the Linux add-on to it through the Deployment Server. Although the logs from this server are being received by the HF (we verified this using tcpdump), when we search the desired index, we don't see any logs in it.
(Our Splunk version is 9.2.1 and UF version is 8.2.9, and due to certain reasons, we cannot use the latest version of UF.)"
There can be multiple reasons.
You're mentioning a HF - do you mean that your events go UF -> HF -> indexer(s)?
Are you getting _any_ events from this UF? (especially own UF's logs into _internal index)
Are you getting any other events through that HF?