While owning an LLC doesn't violate the H1B visa work conditions, working on an LLC does, even if there isn't any reported employment or income to the IRS.
Your current H1B employer probably won't care, but if USCIS ever caught wind of it (even years later) you will likely lose your H visa. USCIS recently closed the loophole where F-1 students would work unpaid internships without using OPT, and are completely unforgiving about visa workarounds.
In other words, if it's genuinely side work.
There's a specific statute to that effect, and they're required to inform you of same.
(I'm not a lawyer either, but I've worked in CA for a long time.)
http://www.leginfo.ca.gov/cgi-bin/displaycode?section=lab&gr...
The gist: Has to be your own time, own resources, and not related to your company's current or anticipated business.
It's that last clause that's the kicker. For some companies, it's easy to prove -- e.g. wood working is probably unrelated to Twitter's businesses. For other companies that literally work on everything (eg. Google/Alphabet)... it's a pain in the ass. Also: Many companies make reporting the IP or side work a stipulation of your employment contract -- ostensibly, so they can claim that it is related to their business in some way. It's right there in Code 2871. :)
PS: IANAL.
I consulted with a business attorney in Silicon Valley on this particular issue when I was considering getting a startup going on my own after hours. She basically said that there is enough "gray zone" in what I wanted to do vs. what I was doing for my employer (although I felt they were really distinct areas of computer science) that if my former employer wanted to go after me they could easily bury me in legal BS.
Whoever can spend the most on lawyers wins...
Of course, with the exception of explicitly-taken leave, its at least intuitively unclear how one defines any time as not "paid for time" of a salaried employee. (There may be case law that clarifies this, however.)
But in general, "salaried" has not been construed to mean "the company owns every minute outside the office."