How to judge whether the device supports Hardware flow offloading?

[takimata]

@VxBox

At present, only the mt7620 hardware supports Hardware flow offloading

As the option says: It needs to be one of the the MT7621 chipsets (MT7621AT, MT7621ST, MT7621NT -- not MT7620!). Please note that hardware offloading is partially broken in 21.02.

other hardware can also support Hardware flow offloading?

Theoretically yes, but not in OpenWrt: as of now, the MT7621 is the only chipset officially supported with the necessary drivers. (Some people are working on support in other chipsets, but that's not officially in OpenWrt.)