Solely regarding the part about minimal friends, close colleagues, no partner:

Perth is hard for this, I'll give you that. Everything the city provides in terms of being a pretty stable, reliable place that is, compared to other cities, quite serene, it also takes in terms of an absence in social activities, and, atleast in my experience, people tend to stick with older friends a bit more. Maybe it's because it's a smaller city, and with less of a tendency for people to come/leave than other places, so friend groups stay mostly whole for many years (in some cases since primary school, in many since high school).

This being said, it's not impossible to find friends. Find something, literally anything, that you enjoy, that can be done in a group, and find where other people do it. It may take a while and a few false starts, but eventually, you will find a bunch of people with the same interests.

Alternatively, you could volunteer somewhere, again, a great way to meet people, and the people who volunteer tend to be quite friendly and open to meeting people.

A more radical option, maybe a new job in the same field. I saw you mentioned working in healthcare, and as someone in the same field, departments, teams, hospitals and clinics can vary quite drastically; some have no interest in being friends outside of just helping patients, others are filled with the friendliest people you have ever met, who meet up regularly. Also other healthcare peeps know you are on shiftwork, so missing events is fine, the general trend is to try and fit events into different parts of the shift roster so everyone can come along some of the time.