All your characters are just you.
Not a self-insert, or an alternate universe you, or even you having time/dimension traveled to the setting.
Just you, as you are, inexplicably wandering the Elven forests or the terraformed moons of Jupiter or the interdimensional wastes. Insist there’s nothing weird about you being there, no matter how many thousands of years in the future or lightyears from earth it is.
Can you explain how this isn’t a self-insert?
I was thinking self-insert as being a character that is clearly meant to be you but with some name/appearance changes to make it less obvious.
This is just you, watching tv in your Pajamas and checking your phone, while sitting in a Dwarven Citadel 2000 ft beneath the earth during the rise of the Old Ones. That’s just where you live ok.
taz has an example of this
Theres merle highchurch who is clint mcelroys self insert. Then theres clint mcelroy the embezzling janitor in the same campaign.