While de-Google'd, /e/ is a fork of LineageOS that is often VERY out of sync from the security updates AOSP offers, and it puts your device at risk of being easily compromised and tracked. It is not a safe bet as a ROM. I would highly recommend against it if you had to choose between the two. Go with LineageOS, as it is closely downstream from AOSP patches.

If you have a Pixel tablet? GrapheneOS over LineageOS.

If not, and those are your options so far: LineageOS.

I do not have a high opinion of /e/OS or Murena. It is LineageOS but "degoogled" which is a meaningless buzzword considering LineageOS already does not contain Google services/apps (you have to install those yourself). Instead it's connected to its own "Murena cloud" which itself uses OpenAI for a speech to text service. But hey, it's not google so it must be okay, right...?

https://community.e.foundation/t/voice-to-text-feature-using-open-ai/70509

It might be opt in (or opt out? dunno) but this sort of thing should not be a cloud thing, it should be a local service.

It also comes with at least one proprietary app built into the OS and their app store offers proprietary apps with some sort of "tracker detection" thing. I do not trust any "app store" that purports to tell me which proprietary apps are "good."

LineageOS comes with no google apps, no cloud apps, no proprietary apps, etc. It's just a perfectly usable AOSP system. It doesn't even have an "app store" but you can install F-Droid on it. I think GrapheneOS is the same (it supports "sandboxed Google services" but it doesn't include them by default)

As far as I know the only options that exist are LineageOS, GrapheneOS, and maybe non-Android Linuxes if you're brave enough. There used to be DivestOS which although based on LineageOS brought several security, privacy, and freedom improvements, but that project has been discontinued. None of these "degoogled privacy OS" LineageOS reskins impress me.

im an employed security professional, grapheneos is the way

I'm really happy with /e/OS and Niagara launcher.

Funny thing, I have the exact set up you're looking to build. I've got a Samsung Galaxy S5E Wi-Fi Tablet with LineageOS installed, and it works like a charm!

I've had the tablet for a couple of years, and it is starting to show its age a bit with the hardware. And I think there's a lack of codecs in the more recent OS updates that have prevented me from playing higher than 2K quality for videos on YouTube or Stremio, but it gets the job done!

fyi: this community is dominated by graphene enthusiasts so ymmv here.

No experience personally with Lineage or eOS on a tablet, but if you end up with a tablet that doesn't have official support from either, I can vouch for the LeOS GSI (generic system image). Minimalist and with all pings to Google servers stripped out.

That said, updates can be hit or miss with the GSI. The gold standard is still the Pixel Tablet with GrapheneOS, no fuss with complicated install and update methods.

Theres a Pinetab 2.

Starlabs has the Starlite which runs linux. You could use a distro with Plasma Mobile and get the tablet experience you are looking for.