What about an LLM to change course and get a new legal specialization, say 10 years in one's legal career?

That's not practical. Specialization 10 years into practising law is typically due to client needs. Nevertheless, some attorneys legislated out of their field (e.g., bankruptcy or statutory limits on damage awards) may find an LLM in taxation as an entree to a different category of business. Possible, but still not practical.

In response to OP's question, I think it's been answered sufficiently. Just wanted to add though, for those applying to Canada: many Canadian law schools continue to use the "LL.B" designation for their law degrees. However, the Canadian system of legal education mirrors that of the United States, meaning that while Canadian law graduates will have a "Bachelor of Laws" following law school, the vast majority of applicants also have a BA/BSc/other first cycle degree. Some schools (the University of Toronto, for example) are now converting from the LL.B designation to JD for clarity that this is typically a degree done after undergraduate studies. On the off note, the original LL.B concept hails from the United Kingdom, where law is an entry-level undergraduate program.

Canadian LLBs also differ from their British (or other international) counterparts, since typically you do need an undergraduate degree to study common law. The difference between the LLB (or BCL - Bachelor of Common Law at McGill) and the JD is just semantics in the Canadian legal system, but the change started because of the perception associated with the old LLB.

It is possible to do an online LLB (university of Manchester is a good one) and a US LLM (can be done online) which is suffucient to get you admitted to the bar in some states, but it won't get you a job or teach you how to be a lawyer in this country. You're better off going to the nearest TTT shithole