Back on the 2000s I remember a period of time where group SMS services were a thing - you could setup a group where any time a member texted a number it would be related to the other members

Power and internet in our town keeps going out but SMS keeps working, so a service like that is suddenly very relevant!

Anyone know of a good option for groups >20 but <100 people?

One of those things that's hard to search for because of all the SEO junk about running a marketing broadcast SMS list

Turns out https://group.me works for this, if you turn on "Enable SMS delivery" for anyone in the group who has also installed and registered with the app
@simon it's ages since I've looked at it, but I think https://www.frontlinesms.com/ might offer that sort of functionality
FrontlineSMS

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FrontlineSMS
@amcewen @simon one of my favourite all time projects because of what it enabled in non internet connected communities
@simon Signal.
@drwho that's no good, doesn't work if there's SMS but no internet connection
@simon group.me is one I remember offhand
@simon group-text? Yeah a pain to maintain the list...
@simon twilio does it, I believe. SMS Forwarding to a group. It’d be a single number that group texts everyone, though, unless you want to do something bespoke to filter out the MO.
@simon it's been a while since I played with these but Gnokii for low level sms stuff, and Asterisk for calls are two projects that spring to mind, though I think Asterisk is still just voip.
@simon an organized calling tree?