Earlier quoted context omitted.
MMS doesn't work on any FOSS non-Android Linux phone I'm aware of, so they definitely do not work for a significant percentage of the population even for basic group text messages. Building an alternative phone OS is much harder than building an alternative desktop OS—the requirements are much higher (battery life, cellular, app support) and the mobile web is far less developed as a stopgap compared to the desktop we…
MMS? Seriously, that's your bar? I haven't had it working on Android or iOS for years , only realising when it accidentally tries to send. I just assumed it didn't work because nobody cared.
My bar for widespread adoption is far higher, but it may be somewhat unattainable and it's definitely not necessary for the types of people who use desktop Linux. Even if you're happy with desktop Linux—in other words, your expectations of integration and proprietary software support are low—you won't be happy with current Linux phones.