To me, partner seems so much less clinical than "significant other".

Partner is good because it says nothing about gender, which is good if your partner does not conform to a gender binary, but also just if you don't want to reveal their gender either to prevent people being weirdos about it—like they often can online, especially if you say it's your "girlfriend"—or to protect yourself if, for example, you're in a same-sex relationship. But it also says nothing too specific about the status of your relationship. Are they your girlfriend? Fiancée? Wife? Something less conventional? If it's not important to the story, why not leave that detail out?

Some languages - specifically Norwegian that I know of, don't have separate words for "boyfriend" and "girlfriend". In Norwegian we have the word "kjæreste" which can be directly translated to "dearest". To me it always feels a little weird to use "boyfriend" or "girlfriend", i guess the same could be true for other non-native english speakers.

My fiancé asked me to start calling her partner because she was sick of being called girlfriend after 8 years

Because she's a woman and not a girl? (don't shoot me, im not english native. But Partnerin is the same)

Personally I (a straight person) use it in an attempt to normalize the term, so that people who want to conceal the gender of their partner have plausible deniability. If all straight people say "girlfriend/boyfriend", then anyone saying "partner" is outed as "a non-straight person trying to conceal the fact".

Some old nuts don't like to hear that I've been living with my girlfriend for years.

Yeah, nobody uses cmalw-lib-2.0

Its deprecated, now we use hack-lib-client-1.17

I wasn’t sure about it either

It ends with them donating money to the malware's creator...

He said the thing!

As a package maintainer, it's a lot of fun sometimes!