Why would store clerks know, lead-free has been mandated for plumbers for almost 40 years?
The trade did not make the change as you say, the EPA did in 1986, personally, I still have a lot of the old solder but I don’t use it although I use copper for my home, I use the lead-free.
“for almost 40 years”
I’m in final stages of restoring a 75 year old home that my grandparents built in 1946. Sweat copper throught, except for recent additions.
I bought what I thought I needed in sweat copper and put together the shower assembly in one of the bathrooms, I burned up a 1/2 lb roll of lead free solder and never could get a leak free connection. So I let one of the contractors helping me use PEX, it was effortless. (The house is a tall pier and beam construction.)
Later I talked with my nephew (was a plumber many years and now works in a plumbing supply house in Sweetwater. He told me I would have to use MAP gas to get a clean bond. I think it was that and the flux.
Note, I am 75 years old.
There are no code enforcements here. You can do whatever you want to on almost everything. I like that.
My family has owned/operated farms in this county since 1889.
Over the years I have seen a lot of bad practices, I try to avoid them.