I've had a couple of forum conversions over 20 years... well more than that:
Matt's BB Script (2001/2002) -> x-forum (2002) -> phpbb (2003-2005) -> vbulletin (2005-2013) -> xenforo
Lots of casualties over the years as you can imagine (most notably The Great Attachment Loss Of 2005) but in the past 10 years or so I've learned to take advantage of 301 redirects (.htaccess on apache, or the conf files in nginx). It's tedious, but not as tedious as updating 1000's of individual forum posts. There is also the possibility of a mysql query to replace data, but that is an activity for pros only!
Edit: hmm, maybe redirects don't come into play here; AMPbot doesn't seem to care if there are dead links, it's more about totally malformed links.... )