You've highlighted a problem that we've been dealing with at Artefactual for about the last year. There's a
thread about our announcement about doing work to replace Elasticsearch, and then there is a later
announcement after the second licensing change about our intention to now stay with Elasticsearch. We had considered OpenSearch and Solr as potential replacements and put a lot of effort into investigating potential changes, but ultimately we chose to stay with Elasticsearch. Our
roadmap highlights our plan for upgrades that will allow us to stick to the open source license. For 2.10 we are moving to 7.10 which is the last release before the change. Then in 2.11 we will move to 8.16+, which is the next release after changing back to and open source license.
As far as timelines goes, we are working on a small 2.9.2 release, which we are about to start testing. Then we will move back to 2.10 release work and hopefully have that out by the autumn, keeping in mind urgent issues or unforeseen work might come up. Then we'll scope 2.11 and start working towards that.