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