I just read the rules and this is my first time commenting here, so whatever I end up typing may not meet the standards of this subreddit, but here is what I found when checking this out myself.

I searched for the 1996 state of the Union address when Bill Clinton (a democrat) was president and Newt Gingrich (a republican) was speaker of the house, to see if it was true when the parties were reversed. It took me even less time to find a time when Newt Gingrich clapped for something Bill Clinton had said. You can see it around here. Just a moment later though when Bill Clinton says the state of the union is strong (what should be good news), Newt Gingrich can be seen not clapping. Right after that, though, he can be seen clapping, so it appears he applauded various stuff as well.

I will add more links as I find some more, so I can give you some better information.

Edit: as I have been informed, my comment needs to deal with stuff more than 20 years ago.

So for even more context, I checked the 1991 state of the Union address, when George H W Bush (a republican) was president and Tom Foley (a democrat) was speaker of the house. It only took about 2 minutes for a very disinterested (or maybe just tired) looking Tom Foley to clap at what George Sr said. You can then see a minute later what appears to be Foley starting to clap the quickly putting his hands back down.. I can't make up my mind about what that was, so I will leave it up to the readers. Again Foley can be seen clapping after something Bush said. That being said, what George H W bush said about Americas finest days not being in the past, is something that probably should elicit clapping from either party, but once again, I can't remember seeing Paul Ryan clap at all, and only smile once.

Going way back in time to the last time since then that there was a democrat president and a republican speaker simultaneously, we go to the time when Harry S Truman (a democrat) and Joe Martin ( a republican) was speaker of the house during the 1948 state of the union address. Footage from this time is limited and difficult to come across (not least because a movie came out in 1948 called "State of the Union") but I did manage to find a video showing part of the Harry S Truman speech. This is more a series of experts than anything, and I will try to find better footage. You can see times when the congress (or parts of it at least) were clapping, but the people behind him were not. If you find it odd that the vice president wasn't clapping, it is important to note that that man was not the vice president, as there was none at the time. There wouldn't be until 1949, when the speaker was once again, from the same party. Also, I believe the speaker was either seated on the left, or the footage was flipped for some reason, because that person looks a lot more like Joe Williams.

So in short, it appears that traditionally, not required to clap at everything the president says if the speaker is a member of the opposing party, it is traditional to clap and Paul Ryan not clapping once is indeed a break in tradition

Edit2: Just found footage from the 1947 state of the union, where Truman received not only applause, but a full standing ovation.

Edit3: I have been checking more of these old speeches, where the Speaker of the House's party was in opposition to the Presidents, all have so far applauded at various times through out the presidents addresses, though not necessarily at all the same times.