A little late to the party so let me know if this answers everything so far:
- ERA does manage adventures: combat, maneuvers, spell casting, resting, criticals, RRs, inventory, traveling, foraging, and maybe more that I'm forgetting. Some things are more useful or complete than others, mostly because features are driven by requests. There was a time when there was more time and some polls where posted which allowed users to guide the content of new versions. Some things that you may see as "missing" where the stuff that no one voted for back then, so it seemed like there was no interest. Any feature with enough interest is added to a ToDo list, which combines time available for new developments, with how easy or hard it is to add. For example, Training Packages were impossible some years ago, but now that we have character inventory, better stat gains, and improved skill development, it is in the pipeline for development during this year.
- ERA can show a map/image to players, although it's crude at best, since it's one of those features that never really took off. The GM can go from the adventure options to the travel module, which is always at: IP:PORT/Travel and an image can be uploaded there on the left side. Some day in the far future, that should add tools for computing distances on the map. in the meantime, please enjoy the calculation of strategic movement on the right.
- The GM can send "secret" messages to the players by using the Herald module. It's also accessed from the adventure options. Messages written there will appear on the character status module. This is where the feature ends, there is no way for the player to write back to the GM.
-ERA for RMU will be a thing, it is already a thing, but it can't be put for sale (even the basic $0 version with examples) until RMU books are up for sale.
- Importing ERA characters in other systems is "allowed", this only requires someone to write/program something in the importing system that reads an ERA character file. We are open to answering any question that helps understand the format.
- ERA can absolutely handle players in different countries, it is being done by many groups. http://no-ip.com has been recommended several times for this on the Discord server. The tools included might be lacking when compared to Fantasy Grounds or Roll20, but this is because ERA is more designed to be used by the GM at the table with the people there, although pandemic times have made that almost never the case.
- Almost (if not all) fields requiring a roll in ERA have a button to allow for random rolling, which also knows the correct dice type in each case, and also handles open ended rolls, just separate them with commas, for example: 02, 96, 38
If you are playing remotely and have a voice chat going on, the player can roll their own dice at their home and just say the number out loud for the GM.
If the players wants not to roll a physical die, but to push a button that makes a random roll, when the GM can do just that on the adventuring module, I'm not sure I understand the request.