Employers certainly don't like that, they want the employer's body and soul 24 hours out of 24. But legally they only own 8 hours of my time and I'm working 12 hours days anyways be it a second job, learning new stuff (programming is hard, gotta keep up) or my own side projects that haven't made a dime so far in 20+ years. Plus with the work from home new world, I shave off just about 4 hours hours from my daily schedule. Otherwise I'd commute some 1.5 hours each way, so 3 hours wasted plus 1 hour obligatory lunch, that's 4 hours. After initially enjoying my new unexpected free time, then trying to make a breakthrough in trading using it and predictably failing, eventually I did the rational thing and got a second, part time (half time) job. Was upfront with the employer that I already have a full time job and won't leave it, so my options were severely reduced compared to just lying and providing fake identification so they can't know I have a full time job. Anyhow made good money as a contractor while it lasted and afterwards made a pause as it's a bit exhausting. Unfortunately it seems the market from a year ago is gone and employers want 100% full time when they don't demand straight return to the office. For now I'll still try for a while to negotiate in good faith but seems that doesn't lead anywhere which leaves me with no option but to go underground. Why is is acceptable to get a second job as a taxi driver, fast food wrapper or what else but when it comes to software development, employers don't seem to grok that their ownership of me ends after 8 hours?
Fake identification? What country do you live in? LOL And I'm not being sarcastic. In the USA, you can't get a job without providing a social security number. Working under a false identity would wreak havoc with your income tax reporting and your retirement contributions. How the hell would you even get paid? You gonna have a bank account under a false name?
I know, reading https://www.reddit.com/r/overemployed/ got me the idea in the first place A year later I'm paying off the leftover mortgage on my apartment, not a trivial sum which I'd have to pay for another 15 years. After they raised my rate by almost 40%! An American friend asked me why I didn't get a fixed rate credit: because they don't exist where I live, certainly not for real estate 30 years credits. So after 15+ years and paying in full the apartment's value I still own 70% of it to the bank . Well not anymore.
In your original post, you did not clearly identify the two jobs you are seeking to hold. Are you trying to work as a software developer for two different companies at the same time? If so, then you have not really addressed the question of who owns your work product. I don't work in IT, but it seems pretty obvious to me that companies are going to concerned that you will use proprietary information, or some parts of something you are developing for them, at your other job. In theory, it should be possible to address that with company policies and the terms of your employment contract. But it practice, it's probably just easier for them to say that you can't hold another job in the same field.
You are a hopeless nutcase. You never wrote a single upbeat post on employment. Constant bickering, yet you never do anything about your seemingly miserable life. It's not even clear what you really want, which seems something you don't even know. 2 jobs but after short time too tiring? Then how about 1 job and doing that with all your best effort and devotion. If you perform well you get eventually promoted and move up the ladder. Worked for many generations, even today. Try it out some time.
Business hours are typically 9 to 6. So both employers will typically want you exclusively during those hours, even if working remotely. To attend meetings and collaborate with co workers using zoom or teams. Freelance project based work that is often a different story. You sometimes get to go off for a few months to deliver some piece of work. And the client doesn't care if you have other projects on the go as long you successfully deliver their work. Things only become immoral if the client is expecting (and paying for) 8 hours a day of work from you but you are doing less. However to me software development always includes think time as well as keyboard time. And there are 18 hours in the day to think, i would even argue that sometimes we are thinking during sleep time as well..(the subconscious is always working away in the background).. So the client/employer always gets way more than 8 hours a day out of us. So I wouldn't feel guilty about doing two jobs and not telling both clients that i have another. Both will be getting the 8 hours they are paying for.