Mailing lists will always be king. I don't get it either, Discord is proprietary, hosting your OSS project's infrastructure there just seems... idiotic.
I'm sad that Hyperkitty, which is in all other respects a good piece of mailing list archive software, lacks a threading view. Now that most FOSS mailing lists have started using it, I've lost one of the main productivity benefits of them compared to linear discussions like chatrooms.
If it's important for me to follow a discussion in detail, I will try to download the emails to open with Mutt, which can be easily configured to use a threaded view.