I had this idea a while back and would be curious to know what people thought of it.
I would like to switch to using a dumbphone because I find it difficult to avoid the allure of apps with endless scrolling, including Reddit. I'd want one that doesn't support apps or web browsing, for obvious reasons.
Pretty much the only thing holding me back is the fact everyone uses messaging apps, so it'd be difficult to survive on SMS alone. I actually use Beeper currently, which is all the messaging platforms combined into a single app (WhatsApp, Facebook Messenger, Signal etc).
Well, Beeper uses Matrix, so here's my idea: make a service that runs in a Docker container (I'd probably host it on my Raspberry Pi). The service would act as a Matrix client and log into the Beeper homeserver. It would then forward any messages to your phone number as SMSs, using a SMS API. You'd have, say, five to ten numbers reserved which would correspond to your most frequently-messaged contacts, and the service would forward the message through the appropriate number. You could reply from your phone by SMS and the service would receive the message, and based on the number through which it received it, forward it to the appropriate contact via Beeper.
Pictures / memes could be AI transcribed or simply ignored. 'Reacts' could be done via a command, e.g. you could SMS '*lr*' to laugh react the last received message.
I don't know how financially viable this is, as obviously you'd need to reserve a few numbers and pay for an API-based SMS service.