Looks interesting, this domain has a lot of players such as Google's coin-or so some quick description of its advantages or a benchmark would promote it better.
Because it’s Java you can use it with all the various libraries and any compatible languages that support Java libs like kotlin and Scala.
Is Kogito ready for production use? Does it have a UI that lets users develop their own rules?
To declare incremental constraints in OptaPlanner, take a look at ConstraintStreams if you want to avoid learning DRL: https://www.optaplanner.org/blog/2020/04/07/ConstraintStream... It's very similar to Java 8 Streams (but incremental and under the hood it uses Drools).
Coin-Or is a separate project. It's the fastest free/open source LP & MILP solver I've seen, but has a terrible CLI if you don't want to use it as a C++ library. It's easiest as part of the Open Solver Excel plugin. Lp_Solve isn't as fast I don't think, but the CLI is much easier to use and better documented. I prefer to use a scripting language language to write my own .lp models and send that directly to the solver. There are lots of libraries to do that, but it's easier for me to write code I fully understand than to try to learn someone's library.
Google has the "Or-tools" solver which I haven't used, but have friends which do use it and like it.
[0]: https://www.coin-or.org/ [1]: https://developers.google.com/optimization/