Yeah both codebases were moving very quickly and by the time the pull requests were compiled and reviewed, both the Lemmy and Hexbear codebases were several commits ahead. It was taking up all the time of an entire core maintainer at Hexbear to manage conflicts and fix pull requests. Meanwhile the site was at the peak of its new launch spike and nearing the peak of the US presidential primary/election cycle, which was r/CTH’s bread and butter. The database was less optimized back then and Diesel did not (and iirc still does not) support cross joins, which was a major detriment to the optimizations Hexbear ended up using
It means that the Hexbear fork is going to eventually be replaced with a slightly modified version of an up-to-date Lemmy. And that process will involve Hexbear community members contributing to Lemmy to try and get some of the Hexbear-specific features implemented upstream