We have a section in our web site on repairing lathen plaster.
The repairs if done properly will last provided no further movement occurs.
You have no control over that. Over time there will be new cracking but that is the same for most buildings.
No one put more effort than me into crack prevention in my new home. But 5 years in and some minor cracking has occured in stress areas. I will wait another year or 2, then repair them.
Any superficial repairs will definitly crack again, the crack has to be dug out and filled properly.
The plywood is not a very good option it will look like ****T
Lining boards will work if you like the timber look but expensive and way too much timber, and would not suit the era.
Another option wich is also expensive but the best option for long term, is to rip out all the lathen plaster and replace with plasterboard. This is a major renovation though!
Cheers Rod Dyson