I am working on a project of upgrading Drupal 6 to Drupal 8.
I have huge data in Drupal 6 site.
I have upgraded the site from Drupal 6 to Drupal 8.
But, views are not migrated.
That would be a big step. I migrated D6 views to D7 and even that was not a smooth transition.
First, install all the modules related to views you have on Drupal 6 site. Then you should have all content types defined as on D6 site. Then export view and try importing it. Most likely you will need to check "Bypass view validation" to finish the process at all (that exists on D7 views import page, not sure about D8). I even had to manually change that export file to make it work at all. At end you will most likely have to adjust views manually. Some view properties will most likely be missing.
Moving to D7 and then to D8 would probably be easier, but there would be much more work for all other stuff, so it's not worth it I guess.
I'm aware that this is not full answer to your question, but if it helped it at least a bit I would be happy. Good luck!