To install OpenWrt in D Link DIR 853 A4 follow the steps.
1- Download DIR 853 A3 firmware below with changed headers to look like its A4 firmware ( Prepared by @kar200 )
https://drive.google.com/file/d/11CRBHCgVRJEIMsBxAMAceLODK3u0WzTT/view?usp=sharing
2- install this through stock firmware web interface. After successful install you can use router as normal, you have to setup wireless manually by connecting ethernet cable to router.
3. After that you can install normal stbale sysupgrade updates of openwrt through web interface.
Current is : https://downloads.openwrt.org/releases/22.03.0/targets/ramips/mt7621/openwrt-22.03.0-ramips-mt7621-dlink_dir-853-a3-squashfs-sysupgrade.bin
I have tested on my device this method is working fine.
Thank a lot to @kar200 for the firmware and @Lucky1 to method for backing up the mtd blocks