There's a hill on DALMAC that most people do just to prove they can. After 20 years' of climbing it, I started doing the bypass route. They bypass actually has more climbing but not the one steep grade, and the roads are in better shape.

I don't see the attraction. A hill is something you climb only so you can enjoy the nice downhill.

Some of these are mountain climbs.

I know I posted up a mountain climb too, but I had in mind the little British hill climb sprints of all-out for like 2 to 4 minutes.

Going to Southern France to do some climbing in Sept for a week with some friends, staying in Bourg d'Oisans - Definitely doing Alpe d'Huez and then other climbs in the area. It will be the most climbing I've done in a week every. A few years ago I did Clingmans dome from both sides, and the first 20 miles of BRP from Cherokee all in the same week for a total of about 12,000 or so.

Is it part of the Vermont Challenge?

Some of the climbs I've really enjoyed the past few years and may do most of them again when the weather gets better:
1) Mount Riga Road ... starts in Salisbury, CT and into MA ... not super steep but goes on for around six miles ... a gravel road that I just love
2) Sunset Rock Road ... also gravel but a harder pack surface than Mt Riga Road but a much steeper grade ... starts in Eastern NY and up into MA. Did a ride last year going up Mt Riga Road, then the pavement descent into Bash Bish Falls (NY) then up Sunset Rock Road ... then, finding my way back to Salisbury.
3) Hope to ride sections of the D2R2 course (Pioneer Vally MA and Southern VT) ... may not ride the organized ride but piece together different sections by myself. Also mostly gravel and relentlessly hilly.
4) If I make it up to Acadia National Park (ME) again, hope to ride the auto road up Cadillac Mountain ... love that ride - gorgeous ocean views!
5) Considering going back out Mount Greylock (MA) ... did it once a few years again but have been thinking about it this winter.

Then, other miscellaneous hills ... can't avoid them in New England.

Not sure. Here are the only 2 sites I've really seen it on. First showed a 2018 event, but when you click on the website link, it only shows a cancelled 2017 event. Cant even figure out how to register for it.

Annual Mt. Equinox Uphill Bike Climb

Skyline Drive - Annual Mt. Equinox Uphill Bike Climb