Well i can say that it is on in my r7800 build.
root@OpenWrt:~# ethtool -k br-lan
Features for br-lan:
rx-checksumming: off [fixed]
tx-checksumming: on
tx-checksum-ipv4: off [fixed]
tx-checksum-ip-generic: on
tx-checksum-ipv6: off [fixed]
tx-checksum-fcoe-crc: off [fixed]
tx-checksum-sctp: off [fixed]
scatter-gather: on
tx-scatter-gather: on
tx-scatter-gather-fraglist: on
tcp-segmentation-offload: on
tx-tcp-segmentation: on
tx-tcp-ecn-segmentation: on
tx-tcp6-segmentation: on
udp-fragmentation-offload: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: on
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: on [fixed]
netns-local: on [fixed]
tx-gso-robust: off [requested on]
tx-fcoe-segmentation: off [requested on]
tx-gre-segmentation: on
tx-ipip-segmentation: on
tx-sit-segmentation: on
tx-udp_tnl-segmentation: on
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: on
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
busy-poll: off [fixed]
But i'm using @quarky build
the build includes qcom-nss-gmac and qcom-nss-drv modules instead of the standard stmmac