It would be interesting to see some data (if it even exists) breaking down the increase in Logan passenger traffic/international destinations etc. over the last 10 or so years between business and leisure. I have a hunch it is split pretty evenly which means both will have to come back for Logan to see pre-COVID numbers.
To a certain extent, you could do that by carrier, destination, and equipment choice. To London for example, Norwegian and Virgin would have mostly been leisure seats, and BA, AA, DL would have represented more of the business traveler market. Hainan tends to have more leisure travelers from china than Cathay Pacific, Level vs Iberia, that sort of thing. Call it business travelers who earn hundreds of thousands of miles yearly on the company dime preferring the legacy alliance carriers.
Equipment choice is also revealing; international routes that cater to more business travelers often call for equipment that tend to weight capacity towards premium cabins; some UA 767s have 46 business class seats and only 56 standard economy seats. The opposite would be true on Virgin, Norwegian or Hainan, which cater to the cost conscious leisure traveller who flies in economy. Most major international airlines have configuration options to choose from when assigning jets to routes and even specific flights depending on the demand mix.
As far as destinations go, some are obvious. Seasonal flights are almost certainly leisure oriented, especially warm weather or ski towns. Some serve local immigrant communities, such as Cabo Verde. But others are less clear and I'd be inclined to say that you'd need to look at each city pair. As in, is Latam to sao paulo business or expatriate serving? I don't know, but here frequency can be revealing. A once or twice a week flight isn't serving business travelers, but a daily or even multiple daily likely is.
Domestically, much harder to say. I'd say frequency and flight timing is the tell; flights that get you in for a day of meetings and home again might be business heavy. But anything that is primarly a hub spoke, is a wrench. Boston, by Massports reckoning, is overwhelmingly an Origin and destination city. But what about, say NYC? Chicago? LA? All hubs, but all with lots of origin and demand for Boston. These would be very hard to parse. (All of United's routes are to their hubs, for example. Only SFO is different, as it is definitely a business route for the equipment choice rationale above - a "ps service", operated on jets with lie flat first.) Delta is interesting, and I don't know how they swing a Hub in Boston, nor do I know much about their ops here about transfer rates etc.
But either way, you won't find many business road warriors on the Frontier, Spirit, Allegiant types. Though, admittedly Southwest has a following amongst biz travellers.