OP invented the International AltGr dead keys layout and this is the story.
There was a replacement in "AllChars" which is still on Sourceforge: https://sourceforge.net/projects/allchars/ but hasn't been updated for a while.
Looks like:
is up-to-date, and if I wrote more, would definitely try out, but these days, either I write the accented character w/ a stylus, type out the LaTeX command, or use the on-screen keyboard via touchscreen.
My point being: wow, I've never thought about standardizing the layout, what a marvelous thought. Not for the general public perhaps, but for some programmers it would be a godsend. The whole terminal is basically non-ergonomic on other layouts. Stuff like ./ is right together on the US layout. Similar for coding. I preach to my fellow developers and they see my point but most won't go outside of what's provided by the OS for some reason.
I don't know enough about other European languages from my "region" to make a more general standard (though I suspect it wouldn't be as simple as creating a single "eastern" one, I doubt e.g. Hungarian and Polish have so much in common) but it's a good idea, something that could be collaborated on.
Commenting on the actual text, his solution for the cedilla is awkward and is one of the first things I disable on any computer, because it is a extremely common letter in portuguese.
> English (of course), Danish, Dutch, Finnish, French, German, Italian, Norwegian, Portuguese, Spanish and Swedish
so basically all using some variation of the latin alphabet.
Without dead keys it is def better, but even then I cannot write in said non-english language with that, instead of using one actual layout for that language, and I do not see why not just change layout. Granted, there are some small annoyances because punctuation marks may change place, but I find that easier to learn than using altgr to write letters.
Altgr-intl is pretty good for when you code and write English most of the time and occasionally need accented letters. If you need to write a lot in your native language it's better to get a local layout keyboard.
UK keyboard layouts suck for writing Portuguese, because they lack convenient ways to type all the diacritics. Portuguese layouts (especially on macOS) suck horrendously for programming (curly braces and square brackets are inordinately annoying to type).
These days, all my physical keyboards are US (ANSI) layouts, and I use the US International (with dead keys) layout exclusively. It's the only relatively sane option that allows me to write both code and all the natural languages I'm liable to write on any given day (read: English, Portuguese, and some random French or German loanwords here and there).
I guess I don't mind it too much because the standard portuguese keyboard layout also rely on dead keys for accented letters, instead of having dedicated keys for them. (Or at least the Brazilian Portuguese layout does, not sure about the European Portuguese layout). So that's just what I've always been used to.
The AltGr approach is much superior by not invading on the keyboard shortcut space.
The main difference seems to be in positioning of different characters on a quick glance?
even the article only talks of european languagues.
someone needs to find a better solution.