Donate to socialist groups and causes, especially ones based in your local community. (Food banks, libraries, arts organizations, community legal funds, or individual mutual aid requests.)
You can phone bank for socialist politicians in order to help them get elected. You don’t have to be a local to do this. I recommend Kat Abughazaleh.
If you have a skill that can be used remotely from within the home, consider volunteering it to socialist organizations.
You can create socialist content, but understand that your stuff is going to be algorithmically-repressed to some degree on any corporate-owned social media.
The ones that come to my mind are:
What about using euphemisms for socialism and such? What about alternative video sites?
You don’t necessarily have to use the word ‘socialism’ to support socialist policies, so that could work.
And yes, while there are smaller platforms like Peertube, they’re just not widely used.