The nexus 10 was pretty much my first tablet and it still works pretty well given that I manually update the ROM every couple of months.
Head over to the XDA Nexus 10 page and search for a ROM. A good thread is this one, which is a port of lineage for the manta. Download the .zip file for the rom and place it in the root of the system storage for the device.
In my experience, the best recovery image is TWRP. Head over to the official TWRP page for manta, download the latest image and flash it to the recovery partition.
To enter bootloader mode: press power + vol-up + vol-down
If it is necessary to flash TWRP then it is possible to do so with
fastboot by first entering into bootloader. Follow the instructions of
the TWRP site.
Go to the OpenGapps page and download whatever flavor is necessary. Note that manta has an ARM processor, so be sure to select this one, and also select the appropriate android version for the selected rom (if the android version is not correct they you won\'t be able to install gapps).
Note that the pico option is quite good, sometimes if a big option is chosen then an error while flashing may arise informing that there is not enough space in the system partition (this space can be increased).
Magisk provides an interface to run android as root. https://topjohnwu.github.io/Magisk/install.html
TODO: do and define
Boot into recovery, wipe system, dalvik, and cache, then head over to install and first install the ROM, followed by the opengapps, and then magisk. Reboot and everything should work.
Remember to check the install instructions of the rom provider, since they may vary from case to case.