Miami Executive Airport (TMB) does not have a passenger terminal lounge, and it was never built to have one: this is a general aviation and business-aviation field in southern Miami-Dade County, formerly known as Tamiami, serving private and corporate aircraft rather than scheduled commercial flights, whatever your reason for checking.
What TMB does have is a genuine business-aviation culture built around fixed base operators, the private terminals that service corporate jets, charter flights, and general aviation traffic with amenities like passenger lounges, crew facilities, and ground handling, but built for that specific kind of traveler rather than a walk-up commercial passenger. If you are flying privately or by charter through TMB, that FBO experience is the closest thing to a lounge you will find, arranged through your operator rather than a card membership or airline program, and it varies from one operator to the next.
For scheduled commercial flights and anything resembling a Priority Pass or airline club lounge, Miami International Airport is the real contrast just a short distance away. MIA is a major international hub with its own established lounge network, including the American Admirals Club for American Airlines premium and elite travelers, serving the volume of connecting passengers that a field like TMB was never designed to handle. The two airports serve entirely different kinds of flying, and travelers should not expect TMB's business-aviation amenities to substitute for a commercial lounge, or the reverse.
If your trip involves general aviation or a charter operator based at TMB, confirm what facilities that specific FBO offers directly, since arrangements vary by operator and can change without much notice. If your trip is a scheduled commercial flight, plan your lounge expectations around Miami International instead, since nothing at Miami Executive changes that picture regardless of which airline or membership program you hold.