Hello,
I had a look at my NR7101 OS , looks like stock firmware is allready based on openwrt.
root@NR7101:/tmp# opkg list
8021xd - 1
QFirehose - 1
QLog - 1
SpeedTest - 1.0-1
agetty - 2.21.2-1
ated - 1
atftp - 0.7.1-5
base-files-ramips - 1-unknown
blkid - 2.21.2-1
btnd - 1
busybox - 1_20_1-5
clinkc - 2.4-1
conntrack-tools - 1.4.3-1
curl - 7.72.0-2
dalcmd - 1.0-1
dhcp6c - 20080615
dhcp6s - 20080615
dnsmasq - 2.78-3
dropbear - 2018.76-4
ebtables - 2.0.10-4-1
esmd - 1.0-1
eth_mac - 1
expat - 1.95.8-1
ez-ipupdate - 3.0.11b8-8
fdisk - 2.21.2-1
fw_upgrade - 1.0-1
glib2 - 2.37.7-1
gpio - 1
hwnat - 4200
ip - 3.15.0-1
ip6tables - 1.4.16.3
iperf3 - 3.7-1
iptables - 1.4.16.3
kernel - 3.10.14-1-2fe324e273a81938182a32568e56e411
kmod-cfg80211-normal - 3.10.14-1
kmod-ebtables - 3.10.14-1
kmod-hw_ipsec_mt7621 - 3.10.14-1
kmod-hw_nat - 3.10.14-1
kmod-hw_wdg - 3.10.14-1
kmod-ip6tables - 3.10.14-1
kmod-ipt-conntrack - 3.10.14-1
kmod-ipt-core - 3.10.14-1
kmod-ipt-iprange - 3.10.14-1
kmod-ipt-nat - 3.10.14-1
kmod-ipt-nathelper - 3.10.14-1
kmod-ipv6 - 3.10.14-1
kmod-lib-crc-ccitt - 3.10.14-1
kmod-mtk-mt7603e - 3.10.14+4.0.1.0-1
kmod-netem - 3.10.14-1
kmod-nf-conntrack-netlink - 3.10.14-1
kmod-nf-sc - 3.10.14-1
kmod-nfnetlink - 3.10.14-1
kmod-nls-base - 3.10.14-1
kmod-ppp - 3.10.14-1
kmod-rdm - 3.10.14-1
kmod-sched - 3.10.14-1
kmod-sched-core - 3.10.14-1
kmod-scsi-core - 3.10.14-1
kmod-usb-core - 3.10.14-1
kmod-usb-storage - 3.10.14-1
libblkid - 2.21.2-1
libc - 0.9.33.2-1
libcares - 1.14.0-1
libcurl - 7.72.0-2
libedit - 20080712-2.11
libeventlog - 0.2.10-2
libffi - 3.0.11-1
libgcc - 4.8-linaro-1
libip4tc - 1.4.16.3
libip6tc - 1.4.16.3
libjpeg - 9a-1
libjson - 0.12-2
liblzo - 2.08-1
libmnl - 1.0.3-2
libmosquitto-nossl - 1.6.7-3
libmosquitto-ssl - 1.6.7-3
libncurses - 5.7-5
libnetfilter-conntrack - 1.0.4-1
libnetfilter-cthelper - 1.0.0-1
libnetfilter-cttimeout - 1.0.0-1
libnetfilter_queue - 1.0.2-1
libnfnetlink - 1.0.1-1
libnl-tiny - 0.1-3
libnvram - 1
libopenssl - 1.1.1n-5
libpcap - 1.1.1-2
libpopt - 1.16-1
libpthread - 0.9.33.2-1
libqmi - 1.8.0-1
libreadline - 6.2-1
libresolv - 0.9.33.2-1
librt - 0.9.33.2-1
libsqlite3 - 3.6.23.1-1
libssp - 4.8-linaro-1
libstdcpp - 4.8-linaro-1
libthread-db - 0.9.33.2-1
libusb-1.0 - 1.0.9-1
libuuid - 2.21.2-1
libxtables - 1.4.16.3
libzcfg_fe_dal - 1.0-1
libzcfg_fe_rdm_access - 1.0-1
libzcfg_fe_rdm_string - 1.0-1
libzcfg_fe_rdm_struct - 1.0-1
libzcfg_fe_schema - 1.0-1
libzcfg_fe_tr98 - 1.0-1
libzcfg_msg - 2.0-1
libzcmd_tool - 1.0-1
libzlog - 1.0-1
libzos - 1.0-1
libzyutil - 1.0-1
libzywwan - 1.0-1
logrotate - 3.7.1-1
lte_srv_diag - 1-1
mailsend - 1.17b15-1
mii_mgr - 1
mosquitto-client-nossl - 1.6.7-3
mosquitto-client-ssl - 1.6.7-3
mpstat - 1
mstc_self_check - 1
ndppd - 0.2.5-1
net-snmp - 5.7.2-1
ntpclient - 2007_365-1
nuttcp - 8.1.4-2
nvram - 1
obuspa - 4.0.0
openssl-util - 1.1.1n-5
opkg - 618-3
pure-ftpd - 1.0.30-1
quectel-CM - 1.6.0.17
quectel-DTool - 1
radvd - 1.8
ramonitor - 1.0-1
redirect_console - 1
reg - 1
rilcmd - 1
rs6 - 1
ss - 3.15.0-1
switch-ramips - 1
syslog-ng - 2.0.10-1
tc - 3.15.0-1
tcpdump - 4.2.1-2
terminfo - 5.7-5
tty_log_echo - 1
ubi-utils-ramips - 1.5.1-2
uboot-prebuild-ramips - 1-0
uclibcxx - 0.2.4-1
udhcp - 0.9.8-1
updatedd - 2.6-1
watchdog - 1
webgui_vue - 1.0-1
wide-dhcpv6-relay - 20080615
wireless-tools - 29-5
zcfg - 1.0-1
zcfg_be - 2.0-1
zcfg_util - 1.0-1
zcmd - 2.0-1
zebra - 0.93a
zhttpd - 1.0-1
zlib - 1.2.7-1
zstun - 1.0-1
ztr143 - 1.0-1
ztr369cmd - 1.0-1
ztr69 - 1.0-1
ztr69cmd - 1.0-1
ztzu - 1.0-1
zupnp - 1.0-1
zyAtcmd - 1.0-1
zybtnchk - 1.0.0-1
zycfgfilter - 1.0-1
zycli - 1.0-1
zyledctl - 1.0.0-1
zysh - 2.0-7
zywifid - 2.0-1
maybe this is helpfull for ip passthrough, which is implementet on nr7101