For a 140m² flat lawn like yours, the YUKA Mini would be my recommendation. It's specifically designed for smaller areas and provides excellent value for money in your situation. The YUKA offers all the core features you need (GPS navigation, app control, reliable cutting performance) without paying for additional capabilities that would be underutilised on your property.

The LUBA Mini, while an excellent mower, comes with features like all-wheel drive and suspension that are more beneficial for challenging terrains with slopes or significant bumps. On your flat 140m² lawn, these premium features wouldn't provide enough additional benefit to justify the higher price point.

The YUKA Mini will efficiently handle your lawn size with plenty of capacity to spare, giving you reliable, consistent cutting results while being more economical both in initial purchase cost and long-term maintenance.

If you decide to purchase, I would appreciate if you use my affiliate link below -
https://uk.mammotion.com/products/yuka-mini-robot-lawn-mower?ref=kd2jxen4
Thanks Mark