Right now I'm using services like Chatfuel.com and Adexpresso with FB ads, however, my conversions aren't great and I've gotten banned a handful of times. Twitter and Linkedin ads have also been hit and miss. I've also signed up for a couple of beta releases of ad networks on the blockchain (Primelabs, et al.). So on the waitlist for those. Source: over 2 years ago

Xibo - Digital Signage which is slowly being rolled out across all of our sites. (I used to be the maintainer of the Ubuntu setup script back in the day). Source: over 1 year ago

Xibo Digital Signage -- Used to managed Digital Signage tvs in the hallways. Gets better with every release. Source: over 1 year ago

/u/slugshead mentioned Xibo. They've discontinued Pi-compatible versions but run on a lot of other things. Player(client) licenses per major version are perpetual, or at least very long. I've seen some weird issues with them, don't know if it's fixed (mostly has to do with display scaling, probably related to the consumer-grade smart TVs I have to run it on). Source: almost 2 years ago

Xibo, FOSS and free if you self host https://xibo.org.uk/. Source: about 2 years ago

There are several roll-your-own. For example, Xibo. To get it totally free, you'll need to fire up a Linux master server, then learn the UI for creating content. Source: about 2 years ago