I think the whole reason for the Imperium is standardization and regulation so that interstellar commerce (and the prerequistite is communication) can take place.
I saw a discussion regarding a MTU with no rule set or setting details specified so was discussing things from that perspective.
I... would argue almost the exact opposite. In that case ammunition should limited to specific make and model of weapon (or some other arcane methodology, system of manufacture, etc) and you wouldn't be able to just go any buy a "box of revolver ammo".
For MTU I like my worlds to be different. So one world might use energy weapons predominantly. Another system might have automatic weapons but six shot revolvers are antiques. The law level in one system might not allow purchase of the ammo.
and so on
So for me, you wouldn't be able to "just go any buy a "box of revolver ammo"" in every city of every world. Not sure what rules support the standardization.
Similarly, I'm not sure many people are making the argument that comm units aren't compatible from system to system
Just my own logic and TU which I don't think breaks any rules. <shrug>
It's all but unfathomable that the Imperium, based on "let the goods flow" would have this as a cornerstone of at least intra-Imperial trade.
So, there is a good argument to made that at the very least, all Imperial bases operate on the same operating standard (and thus network design/hardware). Plus, if you want to do business with said Imperial base - or transmit information to Imperial bases/ships that you need to be able to transmit that data in a format that they can read.
I'm not saying it can't be so.
For me, there is a difference between a standard used in space and starports vs what a world does locally. Certainly many.... darn, can't think of the right word... my english is not the best... a world that has a lot of inter system business and interests will tend to use Imperial, or for a different TU, interstellar standards.
How about a world with a government intolerant of outsiders?
A poor system that perhaps can't afford to put whatever is needed to be compliant in place. Heck, the Imperium left them with a class x star port, why would they subsidize a communication network...
Would a low tech system with a low class starport even have a world wide comm system? Telegraph?
"There are no roads where we're going" would a wheeled vehicle be viable on a high tech world with no roads?
All things I believe likely with the systems that can be generated by the rules as well as published systems.
Certainly not trying to tell you what to do or not to do for your MTU.
Just something to think about.
and it looks like you are seeing some possibilities.
While this might make for an interesting complication at times this certainly isn't the norm
I also don't know how much of your adventuring takes place in space vs an adventure that takes you to several locations on a planet or moon or whatever.
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In my current game I have a world that, by the published 3rd Imperium setting material, is populated by a minor race with high technology.
My additional world details: Since local technology is higher than Imperial standard, for cost, weight, and for more advanced features not possible with the Imperial standards, it may not be compatible. This allows me to come up with some interesting unique items for characters to see and even use but they may not work off world.
They also make "Imperial standard" (things you find in Traveller books) items at high tech for export and use by people that do interact with off worlders. There are also some items that are their local tech with adapters, additional software, or other modifications. This allows me to come up with some interesting unique items that characters can take with them and still be usable.
Some off world devices will be totally unusable on planet outside of the starport. Some devices may work in tourist cities and trade locations around the planet because technology has been put in place for it to work. Some devices may need adapters, software updates, or other modifications to work.
I decided that there would be little reason for them to create or maintain a worldwide (using a now days example) 2G network to be Imperial compatible when they have a 16G network.