Wonderfall Unfortunately almost every available option for forum software is written in PHP. We specifically tried to find something that wasn't but they're mostly proof of concept hobby projects that are already abandoned. Flarum is at least a much more modern take on PHP using Symfony.
Lemmy is a mix of node.js + Rust but a Reddit clone wasn't what we wanted and it has some issues itself. Discourse is a huge Ruby on Rails application which is arguably much worse than a relatively small PHP Symfony project. Discourse is very slow/bloated with a lot of weird design decisions and functionality we don't want. If we wanted a Reddit clone, we could have gone with Lemmy, but it's just not a good fit.
Aside from being PHP, it's unfortunate Flarum doesn't support PostgreSQL but I don't really mind using MariaDB for this. The options with PostgreSQL support aren't very good and avoiding having to maintain 2 kinds of database servers really isn't worth choosing software providing a significantly worse experience.