You can control Sonnof stuff from Home Assistant using the Sonoff integration. Think there is an official integration and a third party one I know of. Then there is a Home Assistant phone app. The problem is that it is a local setup so the app only works locally for free. If you subscribe to the people behind Home Assistant/ESP easy etc. there is an easy encrypted tunnel between phone and home assistant wherever you are. You can do it for free but then you have to set up SSH, Port Forwarding, Dynamic DNS etc. Entirely doable but they provide the software for free and it is cheap so I just pay the fee. I actually rarely use the eWeLink app anymore because it’s more flexible. For example there are loads of non-Sonoff stuff I connect to, like my Google-Nest thermostat and front door and a Zigbee Carbon Monoxide Alarm that has no equivalent in the Sonoff ecosystem.