Substitute for pumpkin pie filling

Puree of chayote with (nutmeg / clove / allspice / cinnamon / just sugar) (however you like it) works well. It's an Asian staple and available around the world in most Asian markets. It has no real detectable taste of its own, it just takes on the flavor of whatever you cook it with or put in it.

If that's not available, you could sweeten a puree of butternut or regular squash and get the desired outcome.

With either method, be careful with your moisture content - you want it to be pretty much the same as pumpkin pie filling for the recipe you want to try.

Whatever you use as a replacement, be careful of the sugar content. Depending upon where you live, try mashed/pureed breadfruit - hope it works

Perhaps a custard would work?

I recently saw a custard pie (just custard, which surprised me a bit as I usually see custard with something in pies), and the texture was fairly similar to pumpkin pie. I also recently saw a pumpkin dessert, with a custard baked in a cleaned out pie pumpkin (flavors overall should be reminiscent of pie, and texture similar, just somewhat deconstructed). This is perhaps not so surprising, since the pie is something like a custard plus pumpkin paste - and I've seen successful pie filling be quite liquid, or quite thick.

You might also think about cream pie fillings - I'm thinking coconut cream pie, or banana cream pie, something along those lines, though if you're inspired by a chocolate cream pie filling, more power to you.

So, if the pie filling (perhaps from a separate recipe) was supposed to be quite liquid, a not-yet-cooked custard filling should work, and cook up to a similar texture. If it was supposed to be thicker, a cooked custard might do well.

Of course, you could also probably substitute pudding of various flavors, or some other kind of sweet mash (perhaps sweet potato, or squash - though that does taste similar to pumpkin, or perhaps some starchy fruit). Or see what you can just add in, like bean pie, or buttermilk pie, or the sweet red bean paste (adzuki bean) that serves as a filling in Asian cakes and pastries.

Overall, when I think of pumpkin filling, I think sweet and starchy and kinda creamy, making custards or puddings a closer substitute than, say, fruit pie fillings (which are sweeter, sharper, a bit tarter). And of course, adding any kind of thick mash should help with consistency, as long as its a flavor you'll like. Go wild, if it pleases you.

Good luck with your recipe