as by title is there any plan to support the V6Plus wan connection type also on RT-BE88U ? Or maybe it is already supported and it needs just to be unlocked somehow ?
A quick search pulls up the official Asus support pages that suggest it's already implemented in dominions where it's used! So, by any chance are you trying to use a router from one country/region in another?
*Absolutely prepared to be completely and utterly wrong on this...