Hi Patks3 and a warm welcome.
It can be very difficult to find your feet in a rural community when everyone seems to know eachother already. You're right when you mentioned joining a group or playing sport as the usual ways to make friends.
The other way I usually try is through work or volunteering. You mentioned you work at the school and I wondered if your colleagues have been very supportive? If you mentioned feeling isolated would they try help?
Soberlicious mentioned creating your own group which I wondered if this feels possible? As a teacher already you have the skills to run an adult class.
Photography is another thing that is my go to even if I'm an amateur. I love local wildflowers and take endless photos in the bush and near home. People I run into will often stop for a chat and to see the photos because it is their passion as well. I also have a blog where I post my photos and it is something I enjoy getting to write to people from all over the world. Is blogging something you have ever thought about? You mentioned getting outside is one of the usual suggestions and I hoped maybe the blogging side might make it slightly different.
Volunteer work is another thing I have always thought helps tie you to your community. Whether it is the volunteer fire brigade, local op shop, church, tidy towns group... There is always someone who needs help.
I'll stop there for now but it would be lovely to hear if you feel any of our suggestions might work for you. It's absolutely ok if they don't it will just mean everyone will have to be more creative 😊.
If you find yourself having a lonely day please know these forums are always here for you. There is a section called the social zone which has lots of lighter discussions you might like to join in.