I interact with these (ER605 and some others) pretty regularly for work. I’m pretty unimpressed considering how tp-link market them, like you point out, for “business”.

We don’t do any ipv6 stuff for clients so no direct experience with that, but I wouldn’t be surprised if they just don’t have proper ipv6 support. They’re so underpowered for what tp-link charge for them and they don’t even have proper firewalls (imo).