Support for the latest OpenWrt succeeded! You can get the latest and greatest here:

https://github.com/biemster/funpeater-openwrt

and use the "Peater QCA9533" Target Profile. I also added a precompiled firmware and toolchain in the files section to this project. I'll try to sync with openwrt/main for a while to have it always up to date, and also get a PR through so that won't be needed anymore

First time flashing goes via UART and uboot again (or if you find another way please comment in the post, over SSH  with sysupgrade should be possible too):

setenv ipaddr <make up an ip>
setenv serverip <tftp server ip>
tftp 0x80060000 openwrt-ath79-generic-peater-squashfs-sysupgrade.bin
erase 0x9f050000 +0x7a0000
cp.b $fileaddr 0x9f050000 0x7a0000
setenv bootcmd "bootm 0x9f050000"
saveenv

After entering the shell the firewall should be cleared first to allow access via SSH or Luci:

nft flush ruleset

and the network config in /etc/config/network can be tidied up a bit:

root@OpenWrt:/# cat /etc/config/network 

config interface 'loopback'
        option device 'lo'
        option proto 'static'
        option ipaddr '127.0.0.1'
        option netmask '255.0.0.0'

config device
        option name 'br-lan'
        option type 'bridge'
        list ports 'eth1'

config interface 'lan'
        option device 'br-lan'
        option proto 'dhcp'

root@OpenWrt:/# 

Also don't forget to disable BPF JIT if you want to use the wireless interface as a monitor:

root@OpenWrt:/# cat /etc/sysctl.conf 
# Defaults are configured in /etc/sysctl.d/* and can be customized in this file
net.core.bpf_jit_enable=0
root@OpenWrt:/#

EDIT: fixing config/network and the bpf jit is now done automatically on first boot, I've uploaded a new frimware image with this to this project page. (also nft flush does not seem to be necessary)