In case anyone missed it (and is interested), LTT recently released their solution for mounting a red dot on a PX4. I know the PX4 isn't super popular but I'm glad to see it getting some attention.
https://www.langdontactical.com/custom-gun-work-ltt-rdo-optic-cut-px4-full-size/
https://www.langdontactical.com/custom-gun-work-ltt-rdo-optic-cut-px4-full-size/