@HistoPol @MartinBe
Signal do provide an apk directly downloadable in their website. You can get it here. https://signal.org/android/apk/
This version auto updates without depending on Google playstore and look like is the version used by people on degoogled phones.
I have personally not tried it though.
The other option is using the signal fork Molly (https://molly.im). The version named molly-foss is what you will need.