The Pi 3A has only 512 MB of memory.
In a recent thread, the latest version of OSMC was running out of memory after a fresh install: Sad face loop on first boot (FS fresh from image) - #11 by dillthedog
With the move to Kodi 19 and kernel 5.10, Sam has dropped support for the Pi 1 and Zero models, both of which are ARMv6 devices. They are also 512 MB devices, so perhaps @sam_nazarko can say definitively whether 512 MB ARMv7 devices are still supported.