There is definitely a bug with the Trip to Kirlic quest. Not sure how others got there but, I will tell you how mine happened. Kate was pregnant when I first started to build the wagon. I had the horse. After Kate started showing, Rick wouldn't work on the wagon because of her pregnancy. After she gave birth, finished the wagon. Both Kate and Claire where beyond fully affectioned and corrupted. Including threesome stuff while Kate was pregnant. We talked about doing going on the trip the next day. Next morning Kate was still in bed, Claire was at the fire place. When I left the inn, nothing happened. Now my quest says "Enter the old boar and introduce yourself".
The item above it is checked off it's the one that says "talk to Kate in the evening". I don't know why the trip didn't initiate, but it didn't and now there is no way to trigger it.
Kind of bummed about it because this is like my four or fifth play through and the only reason I played again was because of that new content.
I know this game well, being playing it since Chyos had the debug button in it before the cheatbook item replaced it. So please don't reply with walkthrough stuff, because I have combed it over and over, and searched the forum here. Others have encountered the same bug in this forum, but have been responded to by people not understanding the actual bug.
For some, you talk to Kate in the evening, and then trip doesn't happen. When it happened to me, I didn't realize it was a quest breaking bug, so I went about other quests. I thought maybe I needed to do the monastery first, or some other quest, losing the save prior to talking to Kate.
Now that I have finished every single other quest, including the ones you have to seek out, I concentrated on The Trip to Kirlic and realized it is broken in my game. So for other's searching this forum for "Old Boar", because of the same. Looks like it is broken.
(Also it's not Pia / Ophilia, I have both of her quests done up to the point that has "not implemented yet" note to them, so she can work for Kate in her absence.)
((Chyos if you do actually see this, it's a great game, not a complaint in the slightest, just reporting a bug here since I am not a patreon user.))