Does anyone have any ideas on how to control a Tuya ecosystem from within the eWeLink environment?
I could theoretically achieve this via sequematic.com, though the server hasn’t been running very smoothly lately.
IFTTT hasn’t worked with Tuya for years… Does anyone use or know of any other solutions?
I doubt I’ll ever see cross-platform integration implemented in eWeLink.
I’m not sure I’d try to make eWeLink and Tuya talk directly to each other. That’s essentially building a bridge between two proprietary ecosystems.
And Tuya is probably one of the most complicated ecosystems to integrate with in the first place. The annoying part is that “Tuya” doesn’t necessarily mean one consistent ecosystem - different devices, manufacturers and Tuya-based platforms can expose rather different functionality, and sometimes devices that are all branded as Tuya aren’t even particularly compatible with each other.
I’d rather put a neutral layer above them. Home Assistant can do that, although integrating some Tuya devices properly is definitely not a piece of cake either. 
Ultimately, that’s also why I think Matter is an interesting direction: the ecosystems don’t necessarily need to become compatible with each other. The devices can simply expose a common interface, while the automation layer sits above them.
And, to be honest, Tuya is probably the ecosystem I personally try to stay away from. I’ve had enough experience with it to conclude that dealing with all the quirks and fragmentation usually isn’t worth the effort for me. “Tuya” also covers a huge range of devices, mostly with low levels of quality, functionality and actual usefulness.
Right, I’m aware of that.
It’s just a situation that arose independently of me. There’s an existing small eWeLink ecosystem acting as the master, and a need for limited control over a few scenes or devices via the Tuya cloud. Home Assistant is certainly an option here, but that would mean moving away from the cloud entirely which isn’t a priority for the owner right now so I’m not going to use a sledgehammer to crack a nut. 
For the time being, I guess I have no choice but to use an intermediary solution, which brings the total number of active clouds to three. What could possibly go wrong.
I control my air conditioning via http://sequematic.com/—or, more precisely, I control the Tuya IR Wi-Fi controller that operates the AC unit. I use eWeLink virtual buttons and webhooks, and I have both platforms paired within http://sequematic.com/ so that I can see my smart devices there. Overall, it works well, though there are a few minor issues; the dropdown list in http://sequematic.com/ has a limited number of rows, so not all devices are visible. Still, it handles simple tasks fine: I manage the main logic in http://sequematic.com/, eWeLink sends requests and sensor data, and I send only the actual commands to Tuya.
Yes, I do much the same thing…
I’ve integrated dual R3 for rolling back awnings using Tuya climate events connecting electrically a Tuya device as input of a sonoff switch, in order to trigger ewelink scenes based on Tuya events. That way you avoid using third party tools
Yes.
I use smarthings from samsung and alexa from amazon.
It works for me already several years perfectly.
You link both accounts to alexa and or to smarthings and you can add routines that control both.