Using serial/by-id is already correct. So the problem is that OS, HA, or ZHA does not detect it after reboot.
ConBee adapters are infamously known to be troublesome during reboot, with the workaround being to reboot again or physically unplug and replug the ConBee adapter.
If you are using the built-in ZHA integration then recommend you buy a newer Zigbee Coordinator adapter and migrate to that after flashing the latest firmware, which is easy if using the ZHA integration, see → https://www.home-assistant.io/integrations/zha#migrating-to-a-new-zigbee-coordinator-adapter-inside-zha
For tips on newer Zigbee Coordinator adapters check out this → Zigbee buyer's guide
Other than replacing it with a newer Zigbee Coordinator adapter there are a few things that you might consider doing regardless which could possibly help make that specific problem less likley:
- Update to latest ConBee firmware → https://github.com/dresden-elektronik/deconz-rest-plugin/wiki/Update-deCONZ-manually
- Buy a powered USB 2.0 hub (not a USB 3.0 hub) with an external power-supply an connect the USB radio dongle via it as that will ensure it always has enough power and as a huge bonus it will also help avoid EMF interference if you can move it some distance from your computer, see example → https://www.amazon.com/AmazonBasics-Port-USB-Power-Adapter/dp/B00DQFGJR4/?th=1
PS: If you said you where using Home Assistant in Docker then I would also have advised you to configure Docker Compose (but you did not so that should not apply to you) → https://www.home-assistant.io/integrations/zha#cant-connect-to-usb-device-and-using-docker →
PPS: Off-topic but recommend following these unrelated tips as well which include the USB 2.0 hub tip and also using a long USB extension cable to help avoid EMF interference → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage