@cwebber After reading this thread: https://forums.ubports.com/topic/11451/cant-install-whatsapp-or-signal-on-waydroid/14
You could probably install Langis or whatever non-gapps version of Signal in waydroid via a custom F-Droid repo. I'd stick to a non-android phone OS with waydroid support at the very least, so you can try this. However it might be worth setting up waydroid on a computer and testing this is still possible first. Might be possible to setup waydroid with a Google-Apps android image as well, but I'm not sure how restricted that is. Unfortunately none of these Signal forks support alternatives to gapps push notifications, though, so your notifications on new messages will be delayed. Hopefully one of these will support Sunup as a push notifications provider someday. I think it should be possible, people in the thread I linked have done something similar before fairly recently.