TrendNet TEW-673GRU and ath79 target

I can not find the TrendNet TEW-673GRU device in the ath79 target. Do I understand correctly that support for this device will end from version OpenWRT 21?

Yes, devices will be migrated away from ar71xx to ath79.

There are no ath79 21.02 RC1s for it either, something's fishy ....

How do that device add in the ath79?

See Porting guide ar71xx to ath79?