Not at all. It's often something some people feel quite strongly about and disagree with each other about.

The gender is often derived from synonyms or etymologically related words. I'm guessing the reason it's "Der Computer" for example is that "Computer" works similarly to e.g. "Trockner" (drier) or "Rechner" (calculator, in fact often the German synonym for "Computer") and these are all male (as generally words ending in -er tend to be).

OTOH it's "Das Steak" (maybe because "Das Fleisch" or "Das Kotlett"?) and "Das Shirt" (maybe because "Das Hemd"?). The fallback generally seems to be "das", i.e. neuter, not male.

An example of something with inconsistent use is "Der Laptop" vs "Das Laptop". Presumably this is because "Der Laptop" is derived from "Der Desktop", which in turn is likely simply a shorthand for "Der Desktop-Rechner", making it male. Even the Duden (the closest thing to a "standard" dictionary in Germany) lists it as "der; auch das Laptop" (i.e. "der" seems to be somewhat more common but both are in use).

Oh. Well romance languages don't generally have a neuter gender so that's not an option.

Not really. In Russian, it's usually follows what it feels intuitively closer to - i.e. if it ends with a vowel like "a", it's likely to be female - Coca-Cola, Nutella, Fanta, etc. If it ends in consonant, it'll be male. If it ends in "o", "e", etc. - probably neuter. Though there could be more complex cases - e.g. I'm not sure what gender would something like "Subaru" assume. Probably depends on implied noun - if it's a "company named Subaru" then probably female, because "company" is female, if it's a restaurant named "Subaru" (assuming such one exists and is not sued for trademark violation) then it's be male because "restaurant" is male. Some speakers would just avoid putting such words into a context where such decision needs to be taken (fortunately, Russian has no articles, so die/der/das is not an issue :) or attaches explicit native noun like "company" or "restaurant" to make it clear.

Some words are kind of gender-fluid too. E.g. a word meaning "hall" was female and neuter in past centuries, and now is male. The word for "coffee" is male in formal/educated speech and neuter is less-educated but (to my despair) rapidly gaining legitimacy speech. Russian is fun :)

For things like the user, you can always assume male, but as with other such assumptions, some people may object to it. In some cases, there is a built-in assumption that male includes female when gender is unknown, but in others it just means male and that's it.

It once was (and e.g. newspapers still generally only use the masculine form) but this is a very political question. At work we are ordered to use e.g. Bürger/-in (others use Bürgerin oder Bürger which is just both forms written out). Sometimes there is gender-neutral word (such as Lehrkraft instead of Lehrer) that is a good alternative.

In Russian, at least, the grammatical gender would correspond to that of the word user - which is always masculine.

In Spanish there's usuario and usuaria depending on the gender of the user.

You can technically construct a female-gendered noun for "user" in Russian as well - there's a generic construct for that - it just looks really awkward.

I see. My sense is that the Spanish one is actually used if you do know the user is female, but of course most software doesn't know the gender and defaults to masculine form.

No, it's not standard practice.