The DS216SE will eventually reach its end of support. [EDIT: it is not as soon as triggered this question originally,* but that only postpones the issue. Also I'd prefer a less restricted access.]
Are there options to install an alternative OS? Preferably a Linux flavour, or a BSD variant. It should not run as a virtual machine within Synology's DiskStation Manager.
The DS216SE is built around the ARMv7 (32-bit, 800MHz) in a Marvell Armada 370 88F6707 SoC with 256MB RAM.
The desired functionality is file server, maybe media server.
Is that possible? Not a dumb idea for some reason?
How to proceed to install the OS? E.g., how to make the DS216SE boot into a installer USB? Windows or Linux machine available if needed.
=========
*For the upcoming DSM 7, the cutoff between unsupported/supported is between ds213 and ds214se. Similar support duration for ds216se places support end at 2023.