The newest officialy supported are the Pixel Tablet and the Oneplus Pads, as of today require very similar "standard" steps to unlock the bootloader (fastboot commands from a pc). This might change months from now (even for older devices after an OEM firmware update) because both companies are worsening their stance towards customer freedom so always check wiki.lineageos.org/devices first
Pick depending on size preference but consider that the Oneplus Pads are a lot faster (and have high refresh screens, official stylus support) compared to the Pixel Tablet.
The older Samsungs are a bit trickier at first, specifically require ODIN or Heimdall, but once you have a running Lineage Recovery they work just as well and become standard unlocked devices, LOS updates and upgrades then work the same. The most recent one is the Tab S7.
I never relock the bootloader on purpose so I don't know which ones allow that with LOS installed.
P.S.: have fun (: