Panther is an open-source log management system, which is also available as a service for a time-limited trial. It is still in beta phase, but it looks promising. You can see the “beta” sign on its opening page: https://app.panther.support/ I tested the time-limited cloud service version, but you can also install it locally, either from Dockerhub, or you can build the containers locally from the source.
Even if it is still in beta phase, Panther comes with detailed documentation. There is a notable exception: while syslog-ng is shown on some of the figures, documenting it is still to be done. This blog helps you to get started with sending logs to Panther, using syslog-ng. You can use either legacy syslog with TLS encryption (still a bit problematic) or the http() destination to send logs to the Panther HTTP API.
Read my blog at https://www.syslog-ng.com/community/b/blog/posts/sending-logs-to-panther-using-syslog-ng