Using en/ei and the -en/-a endings
I noticed that a lot of common words that are feminine and should use ei, such as bok, dør, årstid, klokke etc. are often taught in the course using en, but then some are given the -a definite ending (boka, klokka) while others are given the -en ending (døren, årstiden).
If you are a native Norwegian speaker, what would your recommendation be for using ei and the -a ending? Do you bother? Is it true that most people in Oslo don't use either anymore and just stick to en for everything? Do certain dialects use it more than others? I asked a friend who is a native English speaker but now lives in Ålesund, but he mixes his depending on whichever his girlfriend tends to say (e.g. says jenta, klokka, kua but kvinnen, boken, årstiden). I'm just not quite sure what the best way to do things is!
I don't know any more of the Norwegian tree than what I see in the discussion, since I am Norwegian. But I have noticed that almost all nouns that could be feminine usually gets masculine ending. As the moderators say, all feminine nouns can be written as masculine, so it sure is easier to learn just two genders than three.
However it's not very common to stick to just masculine and neuter gender. Most people in Norway use bokmål for writing, even in areas where the dialect greatly differ from bokmål, it might be just as different from nynorsk in any case. Ålesund has a very pronounced dialect that are considered a very regular and "easy" dialect. Bergen is famous for being a dialect totally without feminine nouns. My dialect of Grenland (the two bigger cities of South Telemark plus the closest areas) has a oral form that are remarkably close to nynorsk if written down. Parts of Oslo (traditionally the West side, Vestkanten) will speak very proper and nice and prefer masculine nouns, other parts (East side, Østkanten) will have their feminine nouns in place much like my own. Certain areas of Østfold has such a strict bokmål that it is actually riksmål (at least in writing), but spoken it is considered a source of public humiliation (the Raymond character). In Finnmark they speak somewhat riksmål with a very singsong tone.
I don't know how much influence the moderators (incubators?) have on preferences like en/ei or how much of it is personal preferences inflicted. Or maybe it's just Duolingo magic. For example it is rather annoying that ei keeps popping up as an alternative for ikke as it is an old-fashioned term in little use, lots if posts on that because ei is usually the feminine article. And my German tree keep insisting that Hähnchen is the word for chicken, and all other sources (including those answering in the discussion) say Hühnchen is the preferred term in Germany (they're both chicken, male and female respectively, but males are usually reserved for barbecue(?!)). I'm just saying you shouldn't rely on Duolingo for everything.
Thank you very much for your help! If it helps at all, both Hähnchen and Hühnchen are acceptable and you will be understood in German. I spent a year living in Switzerland learning Hochdeutsch (not Schweizerdeutsch), and they use the French 'poulet' there instead, though I insisted on using either Hähnchen or Hühnchen and was understood. Same goes for die Brieftasche/das Portemonnaie/der Beutel as terms for wallet or purse. All are acceptable in Hochdeutsch, just pick whichever you remember best.
And I might add that Norwegians will of course understand you whether you choose masculine or feminine, or neuter. Or mixing radical (-a) endings with conservative (-en). It's really difficult to sound native Norwegian anyhow so we all accept a huge number of irregularities in the language and will still understand. After all, we are so used to dialects!
"Bok" and "dør" are words very often seen with the -a ending, as is the Norwegian word for cow (ku, kua). I would say it is less common, at least in Oslo, to hear "kvinna". On the other hand you would often hear "brua" (the bridge) or "klokka" (the watch). In Bergen the -en ending is used also for feminine nouns (-a ending is not really in use there at all).