The last API change seems to have happened in 2018 (see https://github.com/syncthing/syncthing-android/pull/1067) which broke Android 4.0.x support. I have also found https://github.com/syncthing/syncthing-android/issues/564 from 2016, which suggests that Android 2.2 support was dropped at that time. Also, it definitely used to work there in 2014 (see https://github.com/syncthing/syncthing-android/issues/44). I am not sure whether this means that Syncthing should be compiled with an older NDK or whether some other hacks would be required to make it work.
However, this device runs Android 2.1 Eclair, which I have no idea whether has ever been supported by Syncthing. There is also a question whether the GitHub issues are more about the GUI or the binary itself. It is definitely possible to run just the basic Linux ARM binary on Android compiled without any NDK (with some caveats, see https://forum.syncthing.net/t/problems-connecting-to-relays-and-global-discovery/14903).
Thank you for the link, although the requirement seems to be specifically related to ARMv5 though? I am saying this because I have run Syncthing with no problems on an ARMv7-A device with v3.0.x kernel. I have done some research, and the device in question here has an OMAP3621 processor, which is also ARMv7-A, so there is some hope at least.