Manufacturer-refurbished ECOVACS DEEBOT OZMO 930.
The manufacturer is selling for $499 on Ebay, which is a fairly good price, but I used the 'Make An Offer' function and had an offer of $399 accepted. YMMV.
I was tempted by today's Ebay Plus deal (https://www.ozbargain.com.au/node/541032 ) which was the ECOVACS DEEBOT N79T for $149, but was tossing up whether a $149 investment in a fairly 'dumb' robot vacuum would be money well-spent, or whether it would end up being frustrating (like our 2nd gen Roomba that just ended up getting stuck under cupboard doors, and which we got rid of after 3 months).
The OZMO 930 has a number of advantages over the N79T:
1) It has LIDAR, so it can scan its surroundings and not get stuck (as often)
2) It can also mop (including detecting surface type, eg. hard floors vs carpet, and will not mop carpet)
It's not a perfect deal. This deal, for a brand-new ECOVACS DEEBOT OZMO 920 for $699 is a technically superior product: https://www.ebay.com.au/itm/ECOVACS-OZMO-920-Robot-Vacuum-Cl… . The main advantage of the 920 over the 930 are that the 920 can simultaneously vacuum, brush, and mop; whereas the 930 will vacuum first, and then mop.
Of the three options - a dumb vacuum for $149, a smart refurbished vacuum (that can also mop) for $399, or a smart new vacuum/mop for $699, I felt this one represented the sweet spot in terms of value vs outlay vs risk.
Nice thorough post mate with great explanation. Well done 👍