Aight biatches I'm bored at work and started hobbying again. I wasn't looking forward to the import because it looked complicated - you get
an undocumented script with no instructions in there, gl;hf. Off course I then actually read the
documentation which didn't seem as bad.
The other thing holding me back was that
installing Discourse is a pain and takes forever, but as it turns out, installing
the development version is relatively easy, straightforward and fast.
So, did the above, got a recent TLS dump installed in a local database, and started the import. Two days ago
The regular forum import is slow; it goes through all posts one by one and passes them through Discourse's regular code for creating posts (yay, good apis <3). However, that takes forever; I've been running the script for err, about 10ish hours? Half a workday on tuesday, most of the workday yesterday (it's suspended when I close the laptop, lols), and it's at 45%. Mind you, this is in a VM and it seems to only use 1 cpu. Which makes some sense I guess. Anyway, this is probably the most reliable approach, ensuring data consistency and shit - which I'll have to check once it's done (should leave it running overnight this time).
There's also a second option, described
https://meta.discourse.org/t/importers-for-large-forums/61681, which involves a bulk importer that just works on the database directly, starting a background task afterwards to finish things / make stuff consistent.
I think I'll let this import task finish (only 1 error so far), check all the things. Then do it again using the bulk importer. Then I'll probably know enough to be able to determine whether we can actually go ahead with the move.
Whether we still want to is another question, but I'm pretty sure at one point we won't have a choice