Nothing is real rule

Tbh as a young dev without a lot of experience in today's market (added because of some of the comments), you need to have a professional LinkedIn persona, and that's true with many jobs. I can see this being useful for those who can't afford/don't have access to a way to get a good headshot.
That being said I'd be wary of what service you use to make a headshot, because a lot of them will probably use your data to train their AI, and/or steal the data from your cellphone if it's an app
- I would disagree that devs need a professional linked in profile.
  I've never had one, and I've never looked at one for anyone I've interviewed. I don't think I've heard of any of my coworkers doing so either.
  
  I found my current, very nice (for my area) dev job through linkedin. When I applied via services like indeed, I would almost never hear back. I heard back from one company and I didn't get the job.
  I am curious what you would do instead. How do you and your colleagues usually search for jobs? I'm always open to hear about better methods of job searching.
  
  I'd actually argue the complete opposite of OP for developers.
  The picture I use for professional stuff is a shoulder up photo of me in front of a brick wall with some greenery in front of it. I'm wearing a black hat, plain shirt, glasses, and a backpack. I've gotten dozens of interviews and recently a new job with this photo that I've used since 2020. I've even received compliments on it being a, "not fake photo".
  Being too much of a "suit" in the developer world can actually harm your chances IMO. Meta actively tells interview participants to come as they are and outright says to not wear a tie because in their own words, "we care about your abilities, not your clothes". Obviously clean up and look nice, but that doesn't mean you gotta stress about appearance. I've personally done all my interviews in various hoodies and it's never been an issue or counted against me as far as I can tell.
  Obviously fintech and finance is gonna be a little more formal, but I don't personally want to work somewhere where how people dress is anyone's concern.
  
  Same. I've hired for a number of entry level DevOps type jobs, have read through hundreds of resumes, and have never once clicked on a LinkedIn profile. I don't know what point it would serve, considering I expect it to be every bit the carefully manicured presentation that the resume itself already is. If you give me a GitHub link I might take a look, but I don't hold it against anyone for not giving me that either.
- I strongly disagree. Unless you are an actor, an overproduced headshot is more likely to work against you. If you are hot shit, LinkedIn serves as nothing more than a way to keep in touch with your colleagues, who already know you are hot shit. If an employer doesn't know you or recognize anyone in your network, but sees a fake glamour shot like this, they are going to assume that you are a ridiculous person who cares more about image than quality of work.
  If your network is small, highlight your projects and publications. If you don't have a network, personal projects, or papers published, focus on that rather than a glamour shot.
  
  I mean I wouldn't pick this photo, but there are some that look very real that I've seen. Like I said, it's an option. Definitely wouldn't be my first option, but if I had nothing else, it could work if executed properly.
- :: laughs in shabby, bearded, cave dwelling developer ::
  I'm sure it might help for cold contacts (HR first look?) and things like that, especially without a strong background/CV. But in my limited experience nobody cares if you're good and good to work with.
  I say "limited experience" because I've stayed at my last few jobs between 5 and 17 years each. So I've not really been switching that often and therefore usually not actively seeking new positions.
  
  New devs today definitely have to care more about LinkedIn than older devs, most older devs can hop from job to job with referrals from dev friends or something similar. The tech boom and venture capitalist funding of the tech industry is starting to die out, which is making jobs in this industry a lot harder to find. So having something like an incredibly polished LinkedIn and resume can be the thing that make you stand out in the crowd of new devs.
  Once you're established you definitely need LinkedIn less. With the job I have now, I have a few friends who could give me referrals and put in a good word for me, but that was not the case at my old job. And before this job I was a junior Dev so my experience wasn't that impressive.
  
  When I was in my mid twenties I would show up for an interview in a suit with a fresh haircut and a shave. I'd have a copy of my resume and a personalized cover letter.
  Now that I'm in my mid thirties I show up to an interview wearing a T-shirt, with scruffy hair and a poorly managed beard-disaster, closed-toed shoes optional. Then I'm like "Be honest, will I hate working here?"
- I think SDXL has some newish controlnet tools that you could use to do this locally
  
  Controlnet isn't really that suitable, it's better at forcing poses and composition from a reference while with faces you want to force a style from reference into any composition. The newest thing is an IPAdapter (on steroids, which is why it's taking ages (in SD terms) to implement into Comfy/A1111, it's been two weeks and it's still not done...). Reportedly doesn't use any additional VRAM so you should be fine with 4G (if using ComfyUI). Meanwhile go here which uses this which is actually ancient (2018), face detection isn't exactly rocket science in the AI world.
  None of those one-image reference things will ever be able to compete with actually training the unet and producing a LoRA but OTOH that's heavy iron territory. Hit generate a couple more times and choose your reference picture well you'll be fine.
  The kinda disappointing thing is that the approach is rather specialised: It does faces, and faces only, and only does faces well because it only does faces: It contains a layer specialised on facial geometry so you'll have no luck trying to, say, copy a specific belt buckle design over. Having a lightweight way to do that kind of thing in a completely generic manner would be a true game-changer.
  
  Cool, I was wondering about that

"I was going to tell a science fiction story about faceswapping, and mass blackmail. Then the news broke about unethical faceswapping videos, and software designed and marketed for creating them: and I realised the future had arrived faster than I thought." - Tom Scott, Feb 2018
- Here is an alternative Piped link(s):
  Tom Scott, Feb 2018
  Piped is a privacy-respecting open-source alternative frontend to YouTube.
  I'm open-source; check me out at GitHub.

That actually seems kinda useful

This makes me wonder if anyone has tried to pass off an AI generated photo of themselves as a passport photo or some other important official license/document yet. How would that go from a legal-trouble standpoint I wonder?
- "In your photo you must not cover your face, smile, or have more than 10 fingers... "
- A while ago a collective in germany used a software to merge the faces of two people into one photo and used it on their passport. On one hand the idea was to evade facial-recognition software which uses the passports photo. On the other to use the passport to smuggle refugees into europe by plane.
  I am not sure the software was based on Machine learning but would strongly suspect it.
  (Source in German: https://taz.de/Peng-Kollektiv-faelscht-Passbilder/!5534868/ )
- I think the EU is mandating fingerprints now