Used Flickr for a while there (like a decade ago, before the weirdness with changing the licensing and iffy reselling of stuff that was listed as CC) as my archive service and even paid for it to get full-res etc features. I’m not entirely sure what their free tier is like now and how Yahoo’s management has gone (if they stopped messing with the service). It used to be great for communities.
I generally show shots on whatever platform people are on (so FB for most friends - horrible compression & all, Twitter, Tumblr, Google Photos, etc) but in terms of archiving then Amazon Prime includes Prime Photos so I’ve got every shot with the RAW it was developed from (I’m a Lightroom user, but a old version as I’m cheap) up there on the Amazon cloud (unlimited storage for photos is part of Prime so you can dump a 100GB archive up there to make sure a fire at home doesn’t destroy your collection). You can do basic sharing from there with folders but it’s not the best way to present your photos. But they’re your actual photos, not a really compressed jpeg, at a lower res, based on the photo you uploaded (which is an issue with lots of other services, especially the free ones). You can also use an MS OneDrive, Google Drive, etc but I pay for Prime for other stuff so the premium storage is effectively free.
If I was building a proper portfolio site then I’d probably actually use Tumblr, even if they’re not ideal, as I quite like their template stuff (as in writing my own html to make a custom site). But any platform with free storage (up to a limit) and an ok template or two should be good (Blogger would work and you can use your Google Drive storage limits for the photos). I suspect almost no one actually needs to pay SquareSpace etc for that sort of thing, but also I’ve seem more than a couple of people who are clearly ok with paying for that.