Great effort Affinity Team - you are on the right track - keep going!!!
IDML opening results were a mixed bag.
Simple files worked "sort of" ok
16pp, no layers, limited styles
71pp inline graphics, limited styles, no layers - tab alignments were missing
Large complex files with Grep Styles & Multi Layers crashed before completion
320pp, multiple para/object styles, 3500+ images with styles, grep styles, etc
exported from CS2015
One 280pp file opened, but crashed on save as afpub
exported from CS4
Well done anyway - i will download updates as they come available.
(MacPro 6,1, 64GbRam, 1TBSSD, High Sierra, clean load nothing else open)
Suggest stciky threade for IDML and GREP/REGEX Styles