OpenWrt 22.03 changed a lot. To set up ttl in OpenWrt 22.03, pls use the following command
mkdir -p /usr/share/nftables.d/chain-pre/mangle_postrouting/
echo "ip ttl set 65" > /usr/share/nftables.d/chain-pre/mangle_postrouting/01-set-tt
l.nft
fw4 reload
The above command set ttl 65 to all interfaces