I'd like to wear jeans while out riding my bike, because I'm often heading somewhere (e.g., a meeting with a service professional like a dr. or dentist, a sports event, the grocery store, etc.) where I don't want to be wearing tights and changing isn't really convenient.

I normally wear Levi's 550 (Relaxed fit) jeans & I'm a bit fat, with fat thighs, and wear a big waist. I'm not big in the dongle. I've found the crotch space is more than okay for normal activities (sitting still, walking), but has nowhere near enough room for riding, the pointy part gets rubbed and mashed very uncomfortably. If I wear a size too large, so it looks like I'm a kid gangster, the cycling is a lot easier, but I don't want to do that. Who if anyone makes jeans (or another casual-style pant) that have generous crotch space suitable for cycling? I mean, much better than Levi's 550.

511 cargo pants. Duluth Trading Ballroom Pants.

You want a "gusseted crotch". Arborists wear them. Riggs, by Wrangler has some.

+1 on the "gusseted crotch"

I wear Riggs (by Wrangler) cargo pants for work. Plenty of room and comfort for biking, although I need to get elastic bands for my pant legs.

Commuter cut pants by Dearborn Denim (made in the US for a decent price, and lots of sizes)

https://dearborndenim.us/collections...uter-dark-wash

An alternative to jeans, since many people find jeans uncomfortable to ride in: black polyester loose-fitting synthetic sport pants.

I wear thin sport pants in warm weather and fleece in cold weather. Much more durable than jeans, too. I have pairs that are close to 10 years old and still looking good. I think they look a little dressier than jeans, too.

To keep them from riding down in back, I use suspenders, but I move the front clips to just a few inches in front of the back clips, so they're holding up the back of the pants. The front doesn't need to be held up. (That would probably work with jeans, too.)

yep. I wear Duluth ballroom with double stretch fabric.

Kuhl makes pants with guzzets. Some of the styles are very slick looking as well. You can hike right off the Appalachian trail, into a decent restaurant. I live where it gets hot, I like the styles made of thin material. It's strong, yet has room and gives where needed.

My go to are New Balance sport pants. They're cut nicely for cycling though they're not cycling specific. They have a cuff zipper, string tie/elastic wb. For errands, health visits, marketing, etc. I wear them with Leatt spd shoes. Leatts are great because there's sufficient clearance for the cleats. A casual, yet pressed look. Sometime, I'll wear a nice Nike non-specific jacket as well. Most of the time I wear padded cycling trunks. They've got a thinner pad and are more comfortable walking around.

Get Levi(?) to bring the Dockers back. Excellent regular pants to ride in. I rode in them for years.

You can get denim looking jeans but made of Cordura nylon. I have swrve jeans but there are others out there

I like Lucky Brand jeans. They come in a variety of cuts and sizes. I like them for their stretchy denim, though they look like ordinary jeans. I’ve done some 100km rides in these jeans with no comfort issues.

Kuhl makes shorts I wear on the bike, Carharrt does as well. They are synthetic and quick drying and have a call phone pocket on the right leg. I'm sure they make long pants with the same features.

Not jeans... but I am retired and I live Mack Weldon Ace Sweatpants. They do not look like baggy sweatpants... they are tighter, pockets and zippered pocket in back. Really soft and I wear them everywhere. I walk out to the garage and hop on my bike. Ride to the grocery store three times a week. They do not get in the chain, or have my crotch catch on my saddle and does not squeeze my junk. Highly recommended... actually all there clothing is great.

Whatever jeans you go with, consider wearing padded biker shorts underneath.

Jeans in general though, are about the worst choice for cycling.