I tried Signal while Google Play Service was either uninstalled or disabled, Signal won't just work.
@EdwardTorvalds I'm using signal on e.foundation ROM (MicroG) all the time and it works perfectly.
MicroG cannot be installed, as it requires a patch to fake Google signatures. This patch is rejected for example by LineageOS, which is why there's a separate fork of Lineage with MicroG integrated https://lineage.microg.org/
That's the problem of virtually every degoogled Android out there - maintaining support for devices costs money and few people support these projects.
@kravietz very few devices are supported