I own a NAS of the ASUSTOR brand, model AS1002T with an ARMv7 Processor rev 1 (v7l), which is running ADM, its proprietary Busybox-based OS. The version is 4.0.7.RVG1 and there won't be any new updates.
ASUSTOR permits (at least since 2023) the installation of alternative OSes. They have tutorials on their YouTube channel for a few models from 2023 onwards. But my NAS is slightly older.
The NAS only has 2 USB ports and an Ethernet port. For a description of the system, I've found this datasheet (note that I'm not sure if mine is v1 or v2).

Does anyone have experience with installing a new open-source OS on this model? For instance, I understand I could try to install Debian versions from this page (ARMhf). And technically, how can I do the install without a screen port? (The tutorials install the new OS on an USB stick from a live USB stick and access the BIOS first to prevent the boot to the default OS.)