See The first “definition” doesn’t fit the group you’re trying to define. If you’re talking about American (using the US as shorthand)…they are by no means restricted to or feature small business owners, that’s but a small (albeit with outsized power) enclave in the “coalition”. ie you can’t mention small business owners without also mentioning that the largest business owners also may be “libertarians”. Their policy ideologically and thus empirically opposes the working class.
There’s no left wing version of the word, or rather, the proper definition is leftist. What you’re describing seems to be an ideological axe you have to grind with Marxism, or socialism something. Actual libertarianism is simply a school of thought - a collection of philosophies - that prioritize individual liberty (freedom). In other words…it’s a criticism - a way to moderate - a necessary capitalist system. Generally these philosophies aren’t related to American libertarianism/freedom…it’s more of a freedom from rather than a freedom to thing…to oversimplify: leftist (real) libertarians believe power structures shouldn’t impede the (not obstructive and lawful) acts of the people - it’s very conscious of power differentials, while American libertarians believe in an absolute right to individual freedom that may or may not conflict with other peoples’ freedoms - after that point of tension it comes down to functional power (thus it’s antithetical to the proper definition and why the prioritization of power pairs so well with - rather than moderates - capitalism and even fascism). Some of the groups that American libertarians welcome into their coalition are grotesque perversions of the concept - even if they put the small business owners on stage at the convention.