I think this is the three devices you have.
- Install /e/ on a Google Nexus 5 - “hammerhead” – e-0.19 Nougat
- Install /e/ on a Google Nexus 6P - “angler” – e-0.20 Oreo
- Install /e/ on a LG G4 (AR,PX,L,P,T) - “h815_usu” – e-0.23 Pie
At first sight the three devices belong to the “end of life group” referred to in the section End of official support for Nougat, Oreo and Pie near the foot of this week’s Week 36, 2022 : Development and Testing Updates
As an over simplified part explanation:
Now that /e/ has dropped Nougat, Oreo and Pie these devices will probably never be mainstream. Maybe unofficial or self builds will materialise? Unknown.
The significance of “beta” in this context probably arose from a group of older devices developed not so long ago but found too difficult to upgrade to Andriod 10. In the interim it was decided by /e/ that Android 10 is to be the lowest supported Android version. (They were sidelined – personal opinion.)
Generally the Google phones are fairly free of proprietary traps and there are many people of various skill levels using custom ROM with Google devices. You might find accessible documentation. On the other hand LG offers a slightly more recent version.