Don’t try to install sanoid (via apt). It’s just a script that you can place anywhere in your path (along with the relevant config files which also can be put in a custom location if you so desire). So just download the latest sanoid version from GitHub - jimsalterjrs/sanoid: Policy-driven snapshot management and replication tools. Using ZFS for underlying next-gen storage. (Btrfs support plans are shelved unless and until btrfs becomes reliable.) Primarily intended for Linux, but BSD use is supported and reasonably frequently tested. and directly use it (and of course customize the config files).
What you do need for sanoid to work nicely are the following packages:
libcapture-tiny-perl libconfig-inifiles-perl pv lzop mbuffer
So you can:
apt install libcapture-tiny-perl libconfig-inifiles-perl pv lzop mbuffer
Remember that you’re going to loose all these customizations when you upgrade TrueNAS - so keep notes/script-snippets of whatever changes you make so that you can quickly get back to your desired special setup on top of TrueNAS after any upgrade in the future.