Actually, the pronunciation for "ln" is somewhere in between l and n. You cannot really hear any of the letters. For this combination the tongue is placed in between l and n.
You will come across many digraphs like this one in Swedish. Some common examples are "rs", "rn" & "rt"
Nouns ending in "el" are a bit of an exception. Since, as you say, tacking "en" onto the end sounds a bit weird, they just get an n added.
Other examples of this include:
Nyckel - nyckeln (key - the key).
Ängel - ängeln (angel - the angel).
Cykel - cykeln (bicycle - the bicycle).
Triangel - triangeln (triangle - the triangle).
Lymmel - lymmeln (rascal - the rascal).
Bibel - Bibeln (Bible - the Bible).
This is something even a lot of Swedes have trouble with because "ln" doesn't sound entirely natural either. It's not uncommon at all to hear people, even adults, try to shift the letters around to end up with a clean "en" either by just adding "en" or removing the first e and ending up with "fåglen", "nycklen" and "änglen".
The situation is not helped at all by the fact that the word "himmel" (heaven) is an exception where all three forms (himmelen, himlen, himmeln) are considered acceptable.
There are no alt-codes for å on your AZERTY keyboard. Since you are on OSX, one option is for you to add a Swedish keyboard "input source" in your settings which will add a flag icon in your top menu bar for toggling keyboards. If the Swedish keyboard is active, å is found next to P where your AZERTY "^" button is (for many of us, it's a "[" button).
or, instead of adding a keyboard, it is very easy to use the long-press method for infrequent access to special keys. In your case, long-press "A" (where most of us have "Q") and then press "8" when you see the small pop-up listing nine different "a" characters. The long-press takes almost one second before you get the pop-up, so it's not the ideal method for heavy typing.