If you are specializing in a particular stack, building your portfolio site on the stack can make it a good project to showcase. Otherwise, can't beat HTML, CSS and (if you absolutely must) JS.

I'm just building mine at https://cocky-hamilton-69af62.netlify.app/ and am using netlify+hugo+vue+tailwind. Hugo can get a bit unwieldy when there are lots of posts, so I'm looking for a basic cms for it. Ideally I'd have some cms work on a sqlite db, and have hugo generate from it. I'm not so sure that solution exists, but even without it hugo is not a bad option

After building my site in multiple stacks, I’ve come back to WordPress because my portfolio site is also my self marketing site and WordPress is the best for marketing IMO. You get blog post, pages, menus and contact forms. Add advanced custom fields and custom post types and WPGraphQL and some Next.js and you got yourself a JAMStack with complete “no-code” backend.

HTML, CSS, JS

And sqlite

I would also consider using a static website generator like Hugo or Jekyll. But you should avoid to over complicate things too much unless you want to play with a specific technology. React and firebase for a portfolio is not necessary in my opinion.

Yes, I actually do want to have some hands on experience with Next.js. I saw it listed in several frontend dev job postings.

It's the one which works best for you. I'd also recommend using a solution that already exists and then building on it (if you want to)