This season, there are only five NFL teams eligible to appear on HBO's Hard Knocks. Because of rules that prevent teams with first-year coaches, teams that made the playoffs within the last two seasons, and teams that have been featured on Hard Knocks within the last 10 years from appearing on the show, only the San Francisco 49ers, New York Giants, Oakland Raiders, Detroit Lions, and Washington are eligible to be the featured team for 2019 training camp. 

Apparently, you can cut one team from that list. According to Matt Maiocco of NBC Sports Bay Area, the 49ers will not be the team that's featured this season. Kyle Shanahan and John Lynch previously expressed that they did not want to be featured on the show, and as Maiocco notes, the NFL has yet to force a team to appear on "Hard Knocks" against its will. 

Raiders owner Marc Davis has publicly stated that his team being featured would be "disruptive," while Raiders coach Jon Gruden has lobbied for the Lions to be the featured team because he thinks Lions coach Matt Patricia's beard would be a good fit for the show. Patricia has similarly lobbied for Gruden and the Raiders to be the featured team

NBC's Peter King reported that the Raiders are "far and away" the most attractive option due to the presence of Gruden and Antonio Brown, and presumably because this could potentially be the team's last season in Oakland. 

Speaking strictly as a fan of the show itself, it's pretty clear that the Raiders would be the most entertaining team on Hard Knocks. Gruden is a character himself, they just acquired Brown and made several other splashy offseason signings, and they brought in three first-round picks as well. It just makes sense.