I'm a big fan of the OpenForge dungeon tiles for D&D designed by @devonjones, and I've been steadily building out a set of my own. In designing a new encounter for my players, I realized that there isn't yet a Diagonal Cut-Stone tile that includes an arched doorway - so I've gone ahead and integrated the models myself!
This is still a work-in-progress, as I've only finished the 2x2 diagonal tile with a normal-width arched door, with the floor to match. It's designed to fit the standard width door that works with the rest of the arched door designs.
I intend to finish out the set (2x2, 3x3, 2x4, 4x2, 4x4) of Diagonal Cut-Stone Arched Doorways, including the double-width door variations - as I do I'll update this accordingly!
I strongly urge you to check out @devonjones 's Cut Stone series if you haven't already, found here: https://www.thingiverse.com/devonjones/collections/openforge-2-cut-stone-series his work is fantastic, and I'm just adding to the options to increase flexibility :)
Update 1 (August 7, 2021) * Added a 3x normal-width version