I've applied this beta to my router and the VPN is again not working (with SPI firewall enabled) and the IPv6 still not working (PPPoE shared connection with IPv4, Prefix Delegation subnet allocated from the ISP for each client ) .
I've reverted to the previous build ( DIR-882_A1_v1.11B01_for_open_SPI_vpn_noworking_issue_2018_10_12(1012162256) ) which at least has working VPN .
Here's hoping in the final 1.11 everything's going to be OK .