GrapheneOS doesn't support it. If there are no ready-made custom ROMs for it, take a look at Generic System Images (GSI). Due to the lack of cellular modem (I assume), GSI have better compatibility with tablets and should only require:
- Unlockable bootloader
- Project Treble support (check with this app: https://f-droid.org/en/packages/tk.hack5.treblecheck/)
That said, there's still no guarantee it'll all work out. Feel free to ask for any details. I went through the misery of installing a GSI on my Tab A7 Lite since it had no LineageOS support and all of the existing ROMs were also GSI that didn't really fit my tastes.
Also, you're not alone if XDA forums tutorials are incomprehensible. A good majority assume some level of niche knowledge.