Yes, Anbox is working pretty well on Arch Linux ARM [0][1], although I haven't tried Signal specifically.
[0] https://github.com/dreemurrs-embedded/Pine64-Arch/releases
[1] https://github.com/dreemurrs-embedded/Pine64-Arch/wiki/Anbox
[0] https://github.com/dreemurrs-embedded/Pine64-Arch/releases
[1] https://github.com/dreemurrs-embedded/Pine64-Arch/wiki/Anbox