OpenWRT builds for Raspberry Pi 4B // 3B

Working on an art project using rPi 4B computers to feed synchronized video segments to multiple projectors. Found a complete and free software package for this application (Falcon Pi Player) that is accessed through a simple web page interface. We would like to access and run these systems over a private, localized wifi network and thought an rPi running OpenWRT would be ideal.

Tried to install to my spare rPi 3B using the images found on the OpenWRT.org site, but could not get them to burn to SD using Etcher -- kept throwing an error with the file.
https://openwrt.org/toh/raspberry_pi_foundation/raspberry_pi?datasrt=version

Hunting around I found a 3rd party build version for rPi 4B that would burn and function.
<openwrt-bcm27xx-bcm2711-rpi-4-squashfs-sysupgrade.img>
(2020.08.11 release from https://github.com/rehan-kumar/lazyleaf/releases/tag/V0.5-alpha)

This addresses my need, but I was really hoping to put my rPi 3B to use and reserve the 4B models for feeding projectors with their dual hdmi outputs.
?? Can anyone here point me to a working OpenWRT disk image for the rPi 3B model ??
?? Is there any cause for concern in using the third party version for rPi 4B that I found ??

PS:
Searching now, I'm finding very fresh builds for rPi 4B at an OpenWRT.cc site:
https://openwrt.cc/releases/targets/bcm27xx/bcm2711/?C=M&O=D
?? Is OpenWRT.cc legit ?? Should I check out these (10x larger) builds??

Don't use these strange/unofficial sites. Use the official OpenWrt firmware selector:

https://firmware-selector.openwrt.org/?version=21.02-SNAPSHOT