menu has moved: go to network / interfaces -> devices tab: then select a bridge and then go to the vlan config tab.
also note that 21.02 has DSA, which for local partitioning on the router does not require vlan anymore: Mini tutorial for DSA network config
2660 was first supported with 21.02.
Did you by chance import existing config from another 19.07 router? try a config reset. Taking over non-dsa config to a dsa device or cross device import could result in network connectivity issues.
unclear: so you did put 21.02rc4 factory image on it using DLink recovery GUI and then used OpenWRT flash firmware function with a sysupgrade image to go to what version? (21.02rc4 is the newest)