It looks like it is a whole business acquisition so all of the business or nothing. My app business for ios has been around since 2009 so I'm less desiring to part with it. I can part with some apps that are basically feature complete, mature and stable income.
I believe I saw Andrew (founder, operator of MicroAcquire) tweet out that some deals are for partial equity of a company. It's really just a listing page and from there the buyer/sellers are free to do what they want. If you had apps that you want to offload, just list and see what type of buyers approach you. Since there are no listing fees it's no risk (other than your time).
The issue I had with Flippa when I listed a business there is that there are a TON of tire kickers. Flippa has a lot of users, but I'd say many aren't serious buyers. Flippa will prepopulate "inquiries" to sellers with some standard questions (ex. "How much time are you spending on the business each week?" etc). I learned to just ignore any message that contained only those prepopulated messages after a while. At first I spent time crafting responses to them only to be ghosted after that. If a potential buyer can't take the time to write their own opening message, they aren't serious.
If they are generating even the slightest bit of revenue, you'll likely find a buyer and will probably be surprised at the multiples people are paying.
Would it be a 2, 5 or 10 year multiple? None of my apps have subscriptions. They are all purchase for $.99 or $1.99 and supported for ... well, 10 years now. I've moved about 144K
Units in all.