One of the core reasons to use Home Assistant is to avoid cloud services altogether. I understand this may be a corporate decision on Tuna’s part, but ugh it’s so counter to the Home Assistant philosophy 
There is already a solution for this:
Sorry, I should have mentioned that the Tuya Local version of HACS does not meet my requirements
I am doubtful there will every be a fully local solution to this that is ‘blessed’ by the vendor. I have been testing a ‘true’ local mod for some of these devices. I have 10 devices converted and running as reliably as ESP based Tasmota or ESPHome devices I have. It only works for a subset of devices in this universe and requires some sometimes not so easy physical access to the internals of the device for conversion. However for these devices that I have been able todo this for, I am very pleased. There are some smart folks that are creating open SDK’s for the 4 or 5 ESP similar chips that are used in these devices. Lighting fixtures are where I have been finding good luck, there are some nice LED lighting fixtures that I have successfully converted. Have a look at this set of posts on the conversion process of one device, it will give you gauge for the path and what to expect. If a hack can be found to insert these open firmwares via the OTA process of the original firmware, that will really open this up for easier conversion to truly local control of some interesting home automation hardware. Good hunting!
That’s great stuff and I will definitely explore this for some devices. Thank you!
Unfortunately, I’m not sure this will work with the LifeSmart presence detector I’m experimenting with.
That seems to be a device based on zigbee radio, the work I was describing is focused on the WiFi radio based products so far. But once you have some basic open source firmware running on one of these ESP like mcu’s figuring out radios other than wifi would seem possible. Keep an eye on their work.
I saw this ESP32 based presence device today, have a look if you have not already seen:
Been monitoring that one too. I just wish someone made a Home Assistant friendly in-ceiling sensor.