The official Velux integration doesn’t support the Velux Active system (KIX 300). As a workaround, it’s possible to add the devices to HA through HomeKit and share this back as HomeKit devices: Velux - Home Assistant
There is another way: the Velux system is built by Netatmo and uses roughly the same API: velux-cli/velux-protocol.md at 6ccddd868d06badbc972b259d65390d6363ca40f · nougad/velux-cli · GitHub. So, in theory, the netatmo integration could be used, if it was possible to supply a different base path (https://app.velux-active.com/api/) and OAuth credentials (client ID and secret from the Velux app can be found online, it’s not possible to create your own).
Would the maintainers of the netatmo integration be interested in this?
This would give access to Velux’ room sensors which are otherwise only used by the system internally.