I’ve created a cloud-to-cloud integration for Shelly 1 and 2.5 relays. It’s completely cloud-to-cloud so no hub is required. It’s using Shelly’s cloud API. Their cloud API isn’t very well documented, per se, but is mostly the same as their local API (https://shelly-api-docs.shelly.cloud/#common-http-api) with rate limits and different authentication.
It’s super-not-official and only works with the Shelly 1/PM and 2.5, but if anyone else would find it useful I put the code here: https://github.com/SRGDamia1/ShellySmartThingsLambda