I'm using PG 14 and have an application using a custom range with a custom domain subtype. My problem: PG does not do an implicit cast from the domain's base type when used with range operators.
I hit what looks to be the same issue. I reported in here:
David Johnston said that he thought that it was a bug.
My workaround is to typecast the two operands explicitly back to their base types.
I don't think that there's any magic to fix it declaratively. My guess is that you might work around it with a user-defined operator for the domains in question that hides the typecasts in its implementation function. (This has worked for me in other cases for other reasons. But I didn't try that in my testcase.)
