If only this was the case. Sadly not 
Ok, just upgraded from P23 to P26 and wanted to share my results. It went pretty smoothly just a few hiccups. After adding new Homey to account from backup none of my devices worked. I read that in a post that you just do another reset and restore from backup again. Before trying that I just did a reboot of H26. This actually made all but my zwave devices working . . sigh of relief. Now for the zwave I was receiving a node error and since I only have 4 of them I decided to remove and re-add them instead of trying the reset method. Now just need to fix the flows that were associated to the old zwave devices and add the new device flow card in its place. Keep in mind I just did the change yesterday, so limited testing of flows, but all devices work. All in all it was a successful upgrade as far as I’m concerned. 
What about zigbee devices?
after reboot of hub they all are working.
You are a very very lucky man. If you read the posts, lots of others not so lucky.
OK I just did a conversion from an Early 2023 to a 2026, and it seems to have worked.
- Enabled backup on 2023, ensure online backups create cleanly
- USB tool to create local backup of 2023, then power 2023 down again for now
- USB tool to update 2026 - only upgrade firmware
- USB tool to restore local backup from 2023 to 2026 - got stuck on Verifying
- USB tool to restore again - this time it worked
- Power 2026 up - can’t connect. Dammit forgot to adjust Unifi firewall rules - fix that
Everything was there. Zigbee is on channel 25, I think it was on 20 before ? I can’t find the post-it note where I wrote that down
Samsung soundbar wasn’t available, had to redo the SmartThings generate token process, now it seems to be working fine.
Ram is at 4GB, so that’s good 
I thought storage was increased, but checking around it’s the same same 8GB for 2023 and 2026 models. But mine thinks it’s a lot less - only 2.66GB ? Yah, that seems typical.
So all in all, after all the horror stories, especially about Zigbee, this went smoothly. I have no ZWave devices, only Zigbee, Matter and plain Wifi. I have to check everything but the spot-checks are so far all good.
Part of the storage capacity is reservered for a separate partition used for firmware updates. So that part is not available as usable space, which you see in the app.
Doublecheck: Can you add new Zigbee devices and repair existing ones?
Have a Third Reality smart plug - P4SPA1Z - that wasn’t responding. Repair worked fine on it - had to hold button then it was re-added.
I added another spare P4SPA1Z smart plug and it added cleanly. But … I unplugged it to move it to another socket, and it became unresponsive. I had to repair it, which worked fine and it’s back working.
You are lucky that the Zigbee migration seemed to have gone well. How many Zigbee devices do you have connected to your Homey?
So far I have 12 Zigbee, 17 Matter directly into Homey. Then about 10 Aqara devices via an Aqara M100 hub and 15 Lutron Caseta dimmers/switches via a Lutron Caseta hub.
Then your Zigbee network is small enough for Homey to succeed in rebuilding it after a restore. Larger networks seem problematic.
