There have only been 7 times in NFL history that a home team in the divisional round was an underdog (source: Pro Football Reference). Here is a list of the games:
1979-80 #2 Tampa Bay Buccaneers, 4.5-point underdogs to Philadelphia Eagles. Won Game
1981-82 #2 Miami Dolphins, 2.5-point underdogs to San Diego Chargers. Lost Game
1982-83 #2 Miami Dolphins, 1.5-point underdogs to San Diego Chargers. Won Game
1996-97 #2 Carolina Panthers, 3.5-point underdogs to Dallas Cowboys. Won Game
2011-12 #2 San Francisco 49ers, 3.5-point underdogs to New Orleans Saints. Won Game
2013-14 #2 Carolina Panthers, 1.0-point underdogs to San Francisco 49ers. Lost Game
2017-18 #1 Philadelphia Eagles, 2.5-point underdogs to Atlanta Falcons. Won Game
It appears that they were all the #2 seed, beside the Eagles.
Here is a list of the #1 seeds who were underdogs in a hosted game. They all occurred in Conference Championship Games:
1978-79 #1 LA Rams, 3.5-point underdogs to Dallas Cowboys, NFC Championship. Lost Game
1981-82 #1 San Francisco 49ers, 3.0-point underdogs to Dallas Cowboys, NFC Championship. Won Game
1982-83 #1 Washington Redskins, 2.0-point underdogs to Dallas Cowboys, NFC Championship. Won Game
1988-89 #1 Chicago Bears, 2.0-point underdogs to San Francisco 49ers, NFC Championship. Lost Game
1997-98 #1 San Francisco 49ers, 1.5-point underdogs to Green Bay Packers, NFC Championship. Lost Game
2000-01 #1 NY Giants, 1.0-point underdogs to Minnesota Vikings, NFC Championship. Won Game
2004-05 #1 Pittsburgh Steelers, 3.0-point underdogs to New England Patriots, AFC Championship. Lost Game
2012-13 #1 Atlanta Falcons, 4.5-point underdogs to San Francisco 49ers, NFC Championship. Lost Game
2015-16 #1 Denver Broncos, 3.0-point underdogs to New England Patriots, AFC Championship. Won Game
2017-18 #1 Philadelphia Eagles, 3.0-point underdogs to Minnesota Vikings, NFC Championship. Won Game (By a lot!)
Source: Pro Football Reference. Just went through and checked which ones were the #1 seed in their conference.