The Aqara temp/pressure/humidity sensor are definitely stable IF you have a carefully laid out Zigbee mesh AND you don't use any incompatible repeaters, and definatley NO Zigbee lightbulbs on the same Zigbee mesh (Sengled are the exception). They won't mess with your mesh because they're end devices, but they will certainly drop if you don't have the position of the repeaters just right (definitely trial and error) and they also will drop as they start to approach 50% battery (which granted is several months). I had mine performing perfectly for months. Moved one repeater to an outlet just 4 feet closer to the hub and it began to drop regularly. Moved the repeater back to its original location and the stability returned.
I have only one of the Aqara temp/pressure/humidity sensors, but I have Aqara leak sensors and one remaining Mijia motion sensor still directly paired. Only the temp/pressure/humidity sensor ever drops and it's only when the battery nears 50%.
However, if your greenhouse isn't attached to your house (e.g. You need to get that signal to travel more than 30 feet open air from either the hub to from the last powered repeater, and you need a few of them, I'd tend to agree with @aaiyar's recommendation for the Konke. The guys that have them say they are very solid.
It's going to be a lot less restrictive to set your Zigbee radio to channel 15 or 20 and use the Konke then it is going be, having to use ONLY Xiaomi compatible repeaters like I have to (I'm using three IKEA Trådfri repeaters - Two outlets and one dedicated repeater). I understand the need for portability and battery power in a greenhouse, but if you have a situation that you can use one of @iharyadi temp/pressure/humidity/luminance sensors, those are excellent. I'm using one as the reference humidity for my Xiaomi Aqara temp/pressure/humidity sensor in my bathroom, so that the exhaust fan turns on automatically when someone is in the shower, but still takes the sticky summers we have here in Toronto into account.
I wouldn't ever buy the Xiaomi Aqara or Xiaomi Mijia devices from Amazon unless the price was much better than you're seeing. I have always bought from either Bangood or Gearbest. During non-pandemic times, I have chosen the Canada Priority Line delivery option for just a few bucks. I almost aways received them within two weeks. Right now, don't know what you'll get. Some buy from AliExpress too, but I personally don't like using them because they don't take PayPal. Since you're in Canada delivery is going to be a problem from China and Hong Kong right now.