The biggest pain these days is that most passports and visa applications still require a physical, paper photo - preferably on real wet process photo paper. Or at least on high quality photo printing paper.
I used to use a certain online passport/visa photo editor that had sizing and options to different photo paper sizes, but that service is no longer free at all to create a downloaded photo. The following was I've used more recently, although I believe there are other services and some applications that can also do on a computer, phone, or tablet. They have an option for submission to a partner that actually prints, but still have a basic download capability. I plan on using the 6 2x2 prints to a 4"x6" print.
https://makepassportphoto.com
My only issue I've heard is that some places see what the content is and either refuse to release it to the customer or perhaps insist on charging for a passport photo price.
It's also been a while for me since I've prepped a passport photo. My go-to place used to be Target, where my closest locations still had real wet process photo printing on high quality Kodak paper. Then (after my local store got rid of their wet process photo printing service) I switched to Costco, which used FujiFilm paper that was about the same quality. I hadn't done it in a while and I went to Target (maybe 5 years ago) where they had a photo printer and charged maybe 60 cents for a 4"x6" print but the State Dept accepted it. The print didn't really look all that good but they accepted it. That was the time when we went to the San Francisco Passport Agency and I recall the clerk looked at the photo and said it might be a bit iffy because of the color balance of the print, but in the end it was accepted and looked OK on the passport and passport card.
My parents have been asking me to help and I said maybe Costco but didn't pay too much attention and didn't notice that they no longer have (since 2021) onsite photo services. They apparently work with Shutterfly now where prints are delivered. But before, my wife went there a few times to get passport photos for maybe $5 for a set of two. They had a setup similar to what the State Dept recommends, which is two front flashes and a fill flash in the back to wash out any shadows. I remember I got a similar effect by taking a photo outdoors against a solid white background.
I'm going to see if this works out - whether CVS or Walgreens will take it. They don't seem to have minimums or separate order fees.
I tried a few things including an app for my iPad. It looked pretty good and was supposedly free, but it was only free for making a single photo that I suppose could be used for an online passport/visa application. To create a print they want $10 to "unlock" color.