There is no industry standard really. And everybody will tell you something slightly different.
There are people getting jobs with portfolios with 80+ pages. There are people getting jobs with 4 pages of pdf-“teasers” and a link to their website.
Personally I find both of them lacking. A long portfolio will very likely not be appreciated. People will start skimming after 15-20 pages once they see the pdf-page count. The teaser thing also rarely works out perfectly in my opinion because the pdf is what will be handed around when reviewing portfolios. The minority of people will have the patience to actually click through to your website/behance. Many people who mainly work with emails just want to see the real and whole thing in their email-software.
Personally I think around 30 pages is a good length with around 4-5 projects. I think that hits the sweet spot between being able to show range and depth without overloading the viewer with useless, crushing input. After all it is also a designer’s job to curate a relevant selection. But again, other people are successful with other things.
There is also this common platitude of “showing mostly process” - while not wrong at all mostly the same people will get upset at you for not showing enough “polish”. While it intellectually might feel wrong I would still advice to try to achieve “polish” over showing “authentic process”. Especially non-designers really don’t have a lot of appreciation for the latter. And there are very often at least a few non-designers judging your portfolio at some point. If you are able to pull off to let your authentic process look polished you have a winning portfolio.
And another tip: After being sucessfull with your ~30 page portfolio bring a longer one to the interview that has ALL the content. Most people in the interview will appreciate that you will show them something that they haven’t seen before and if you are there in person you can guide much better through a greater depth of work. Are they asking a lot of process questions? Show them all the process stuff they haven’t seen before. Are they mostly interested in pretty pictures? Show them all the pretty renderings of the final thing and skip through the other stuff.