Now that Truenas Scale supports just plain Docker (and it's running on Debian) I think it's a great option for an all-in-one media box. I've had my complaints with Truenas over the years, but it's done a really great job at preventing me from shooting myself in the foot when it comes to my data.
I believe raidz expansion is also now in stable (though still better to do a bit of planning for your pool before pulling the trigger).