The lemmy.ml instance has some controversies regarding its maintainers, which may have an impact on adopters. programming.dev seems safer for now, for programming communities; I just hope that it's a well-maintained instance.
Sharing from my personal experience โ with the Typelevel libraries, you don't really need monad transformers if you don't like them.
For dependency injection, personally, while being a big fan and contributor of Typelevel, I prefer to use Scala as an OOP language, too, as OOP is already great for dependency injection. And I'm always surprised by the lengths people go to avoid passing parameters to constructors or to functions. Although I will say that the use of Resource for managing the lifecycle of resources is a Scala super-power.
For errors, there are different approaches, no one size fits all, but personally, I never use EitherT or OptionT, and that's a false choice being presented by these 2 communities. You don't have to pick between EitherT or ZIO because you can choose neither.
Domain / input errors have to be designed with care, and you usually don't need short-circuiting for those. And as an alternative, what you can do instead is to design errors out of existence. I'm sharing some design advice for that here: https://alexn.org/blog/2022/04/18/scala-oop-design-sample/
The effect system is pretty foundational. Libraries built on Cats-Effect can be used with ZIO (with caveats), due to the exposed type classes, but ZIO libraries can't be comfortably used alongside Cats-Effect-driven libraries. You tend to pick either one ecosystem, or the other. Picking both creates a mess, and you need strong leadership that can keep clean boundaries between the modules of the project. We see that in our $work project by combining Typelevel / Cats-Effect libraries with Akka, but there the separation is cleaner because Akka has a clear purpose in our project, without much overlap with the used Typelevel libraries.
I may be biased, but Typelevel libraries interoperate better with the rest of the ecosystem, and they are more mature, but I'm also certain this depends on personal experience and the projects we've been working on. In other words, it's fine to pick ZIO, if you like it better, the problem is with combinations, IMO.
๐ I hope this will take off
I think people fear a problematic "BDFL". On the other hand, the beauty of FOSS is that it can be forked in case you don't agree with the current owners.
I heard that Lemmy is the second most popular software on the Fediverse, and choosing between Lemmy and kbin doesn't have much impact due to the interop (although I hope to see tools for easy migration, if needed). What matters is how well the instance is maintained, and the community.