Dell enterprise series of desktops (Optiplex and Precision) are upgradeable with off the shelf parts. The CPU, RAM, SSD, GPU, Network cards, etc. The same way a regular motherboard from any manufacturer does.
For example an Intel Core 8th gen system would POST with any 8th Gen CPU, any type of DDR4 ram and would boot from any disk. You cannot upgrade an 8th gen to a 12th or 14th gen from any brand, the only proprietary properties of these systems are the case or motherboard form factor and the power connectors.
Dell enterprise series of desktops (Optiplex and Precision) are upgradeable with off the shelf parts. The CPU, RAM, SSD, GPU, Network cards, etc. The same way a regular motherboard from any manufacturer does.
For example an Intel Core 8th gen system would POST with any 8th Gen CPU, any type of DDR4 ram and would boot from any disk. You cannot upgrade an 8th gen to a 12th or 14th gen from any brand, the only proprietary properties of these systems are the case or motherboard form factor and the power connectors.