I own a bunch of them, generations five through ten, and have always had a love/hate relationship with them. None has ever died on me. My main workstation at home, as well as two "homelab" servers are NUCs. They Just Work under both Ubuntu and Proxmox.

The love is for them just working. The hate is for Intel :-)

What they got wrong:

• cooling. CPU cooling is finely tuned and controllable through the BIOS, no qualms there. The disk and the NVME SSD have no cooling whatsoever. Sticking an small 40mm fan to the side and running it at the minimum RPM drops the case temperature from 60°C to 40°C and avoids the NVME SSD burning out. Needless to say, a glued on fan looks fugly.
• opening. By refusing to let their firmware be accessible to the fwupdmgr mechanism, Intel forces its Linux users to physically go to the machine, stick in a USB thumbdrive, keyboard and a monitor, and click their way through the BIOS update. In contrast, my Dell gear gets updated online through fwupdmgr, and I just have to suffer a reboot with a few minutes of downtime. I don't even have to be at the keyboard.
• remote monitoring. I bought two NUC's with vPRO support, to allow for remote management. But the remote console sucks eggs even from a Windows management station, so I wound up disabling it on all of them. Both Dell's iDRAC and HP's ILO run circles around vPRO based remote management.

That's not a lot to go wrong for such a big endeavour, which is why I will keep hating Intel and sorely missing the upgrade opportunity. Just hoping Dell will step into the void.