I know firefighters and machinists heavily using it, the only places I see slower adoption is purely because of bad leadership- exclusivity contracts with certain providers or just plain fear.
What are these firefighters and machinists using it for, exactly?
Firefighter made software to trade shifts across departments, something that was previously asking your friends to ask their friends if anyone could cover them, now everyone can just pose a shift they'd like covered and can trade. Machinist used it to find a special, old and pretty rare lubricant for a tool that you can't buy online anymore. It saw a shop going out of business with a similar tool, he called the guy and was able to buy some. Also custom scheduling software for the shop, to fit around their way of doing business, where all the commercial software options were mostly for large quantities and defined schedules. Also, they had been going back-and-forth with a wordpress-based agency for two years on a website. I made a new one to their liking and got it deployed on cloudflare for free within a day- and they can make minor edits.