That is correct, at least until developers that the Desden Elektronik company employee adds support for the missing/needed “install code” feature via a firmware update, see → Does deCONZ serial protocol for ConBee/RaspBee Zigbee Coordinator adapters not support joining/pairing via install code and qr code? · Issue #20 · dresden-elektronik/deconz-serial-protocol · GitHub
Until then the best workaround is to instead just buy a brand new Texas Instruments or Silicon Labs based Zigbee Coordinator radio adapter/dongle (that has their newer Zigbee radio chips which support newer more modern firmware) and then simply migrate your Zigbee network to that new adapter/dongle.
If you are currently using the Phoscon/deCONZ or Zigbee2MQTT applications as your Zigbee gateway application then it is unfortunately only possible to do partial Zigbee network migration (and even that not fully seamlessly), but it is possible to do a fully seamless migration if you are already using Home Assistant’s own native ZHA integration as long as you first upgrade to latest ConBee/RaspBee firmware. See → https://www.home-assistant.io/integrations/zha#migrating-to-a-new-zigbee-coordinator-adapter-inside-zha
Otherwise you could try performing a two-step partial migration if using Phoscon/deCONZ or Zigbee2MQTT as then you can first migrate to Home Assistant’s own native ZHA integration, but be warned that will only be a partial migration that require repairing some devices and reconfiguring all automations that use any of them, checkout these migration guides → https://skyconnect.home-assistant.io/zigbee-migration-selection/
As for which dongles you should buy I recommend Home Assistant SkyConnect if both want to sponsor Nabu Casa development and like something that is very easy to maintain as long as using Home Assistant’s own native ZHA integration, otherwise recommend that you check out both ITead’s “Sonoff Zigbee 3.0 USB Dongle Plus” (model “ZBDongle-P” which is best for Zigbee2MQTT) as well as their other variant which is “Sonoff Zigbee 3.0 USB Dongle Plus V2” (model “ZBDongle-E” for ZHA). Note that if you plan on using Zigbee2MQTT (Z2M) then currently only Texas Instruments CC2652 or CC1352 based adapters are recommended.