You can install Aurora Store and then download signal v5.51.7 same version on Google Play Store.
First install F Droid:
Then search for Aurora Store:
https://f-droid.org/en/packages/com.aurora.store/
And then search in aurora store the Signal app.
With this you will have the latest Signal version
PS: If you don’t want to use FDroid you can install Aurora Store from AppLounge