Not sure if you consider this is a bug, just sharing my experience:
I migrated my site using the BC to Treep Auto Migration tool.
I was using ‘elseif’ in some of my liquid on the original BC site, which works on BC.
This arrived on the migrated Treepl site still as ‘elseif’, which fails in Treepl.
I needed to manually change instances from elseif to elsif
I imagine this should be part of the auto migrators job, and perhaps needs to be updated?