Can anyone tell me why the FW build I attempted for a GT-AX6000 tanked?

[slackjaw99]

So I've made a couple attempts at a successful FW compile for the GT-AX6000. This last attempt was with the 388.1` branch in Multipass Ubuntu (focal) on an Intel Mac. The first 4 errors are very cryptic. i thought I had gotten all the typos out and right deps in, and the build ran for well over an hour before taking a dump and barking about some "netfilter" code problems. My end goal is to be able to compile custom programs for my AX6000s, which isn't going to happen without me getting the firmware build successfully navigated. I did not build as root. Should I have? Code and environmental params below (cmd$: make gt-ax6000) TIA!

CC net/sched/ematch.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/runner_sdev.o
net/netfilter/xt_mark.c: In function ‘mark_tg’:
net/netfilter/xt_mark.c:33:32: error: dereferencing pointer to incomplete type ‘const struct xt_mark_tginfo2’
33 | skb->mark = (skb->mark & ~info->mask) ^ info->mark;
| ^~
net/netfilter/xt_mark.c: In function ‘mark_mt’:
net/netfilter/xt_mark.c:48:27: error: dereferencing pointer to incomplete type ‘const struct xt_mark_mtinfo1’
48 | return ((skb->mark & info->mask) == info->mark) ^ info->invert;
| ^~
net/netfilter/xt_mark.c: At top level:
net/netfilter/xt_mark.c:56:27: error: invalid application of ‘sizeof’ to incomplete type ‘struct xt_mark_tginfo2’
56 | .targetsize = sizeof(struct xt_mark_tginfo2),
| ^~~~~~
net/netfilter/xt_mark.c:65:27: error: invalid application of ‘sizeof’ to incomplete type ‘struct xt_mark_mtinfo1’
65 | .matchsize = sizeof(struct xt_mark_mtinfo1),
| ^~~~~~
make[6]: *** [scripts/Makefile.build:303: net/netfilter/xt_mark.o] Error 1
make[5]: *** [scripts/Makefile.build:565: net/netfilter] Error 2
make[5]: *** Waiting for unfinished jobs....
CC [M] ../../bcmdrivers/opensource/net/wfd/bcm94912/wfd_dev.o
CC [M] net/sched/sch_hfsc.o
CC net/sctp/stream_sched.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/rdp_ring.o
CC [M] net/sched/em_cmp.o
CC net/sctp/stream_sched_prio.o
LD [M] ../../bcmdrivers/opensource/net/wfd/bcm94912/wfd.o
CC net/sctp/stream_sched_rr.o
CC [M] net/sched/em_nbyte.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/enet_ethtool.o
CC [M] net/sched/em_u32.o
CC net/sctp/stream_interleave.o
CC [M] net/sched/em_meta.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/../shared/bcmenet_ethtool.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/enet_extlh.o
CC net/sctp/proc.o
CC [M] net/sched/em_text.o
CC [M] ../../bcmdrivers/opensource/net/enet/bcm94912/bcmenet_ioctl_compat.o
CC [M] net/sched/em_ipset.o
CC net/sctp/sysctl.o
CC [M] net/sched/em_ipt.o
CC net/sctp/ipv6.o
AR net/sched/built-in.a
LD [M] ../../bcmdrivers/opensource/net/enet/bcm94912/bcm_enet.o
AR ../../bcmdrivers/built-in.a
AR net/sctp/built-in.a
make[4]: *** [Makefile:1081: net] Error 2
make[4]: Leaving directory '/home/ubuntu/git/asuswrt-merlin.ng-388.1/release/src-rt-5.04axhnd.675x/kernel/linux-4.19'
make[3]: *** [Bcmkernel.mk:83: default] Error 2
make[3]: Leaving directory '/home/ubuntu/git/asuswrt-merlin.ng-388.1/release/src-rt-5.04axhnd.675x/build'
make[2]: *** [build/Makefile:509: kernelbuild] Error 2
make[2]: Leaving directory '/home/ubuntu/git/asuswrt-merlin.ng-388.1/release/src-rt-5.04axhnd.675x'
make[1]: *** [Makefile:5849: bin] Error 2
make[1]: Leaving directory '/home/ubuntu/git/asuswrt-merlin.ng-388.1/release/src-rt-5.04axhnd.675x'
make: *** [Makefile:6053: gt-ax6000] Error 2
ubuntu@focal:~/git/asuswrt-merlin.ng-388.1/release/src-rt-5.04axhnd.675x$

After some pain figuring out which docs were obsolete I thought I had all the dependencies covered.
relevant .profile vars:

sudo dpkg --add-architecture i386
sudo dpkg-reconfigure dash
sudo apt update

SHELL=/bin/bash
TOOLCHAIN_BASE=/opt/toolchains
D_LIBRARY_PATH=:/opt/toolchains/crosstools-arm-gcc-9.2-linux-4.19-glibc-2.30-binutils-2.32/usr/lib
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/opt/toolchains/crosstools-aarch64-gcc-9.2-linux-4.19-glibc-2.30-binutils-2.32/usr/bin:/opt/toolchains/crosstools-arm-gcc-9.2-linux-4.19-glibc-2.30-binutils-2.32/usr/bin

sudo apt-get install libtool-bin cmake libproxy-dev uuid-dev liblzo2-dev autoconf autoconf-archive automake bash bison \
bzip2 diffutils file flex m4 g++ gawk groff-base libncurses5-dev libtool libslang2 make patch perl pkg-config shtool \
subversion tar texinfo zlib1g zlib1g-dev git gettext libexpat1-dev libssl-dev cvs gperf unzip \
python libxml-parser-perl gcc-multilib gconf-editor libxml2-dev g++-multilib gitk libncurses5 mtd-utils \
libncurses5-dev libvorbis-dev git autopoint autogen automake-1.15 sed build-essential intltool libglib2.0-dev \
xutils-dev lib32z1-dev lib32stdc++6 xsltproc gtk-doc-tools libelf1:i386