Scoutbook lets anyone – including Scouts who have registered with Scoutbook – email anybody else in the troop and it enforces 2-deep contact. You can’t send an email to a Scout nor can a Scout send a message to an adult without including another adult on the message.
Other options recommended on this thread on Facebook
Google Chat for Troop Committee, each patrol, ASMs
Band App – free, ad-supported communication tool. 6 or 7 recommendations, maybe second most recommended. Even the scouts use it to communicate and post pictues.
Remind – used a lot by schools
We use Remind App. It’s used by our local school district so the kids already have it. One of our Scouts set it up as his Eagle project. We have 55+ people currently on it.
Texts via Scoutbook. Scoutbook uses email to the cell provider, so email@example.com or something similar to that. You have to get each person to verify their cell phone with Scoutbook and also determine who their carrier is. https://phonevalidator.com/ helps with the carrier
GroupMe – probably the most recommended, just slightly more than Band
WhatsApp – usually for adults with one of the other apps for Scouts
Verizon Message+. You don’t have to be a Verizon user to use it. You can create text groups that you can move people in and out of.