I don't know whether what I use qualify as "platforms" or not, but I use a number of social media sites...which I define as those having some sort of interactive community forums. To me a "platform" is something that is all-encompassing, like Facebook...which tries to be the internet all on its own...they'd be entirely happy to have users remain there and never go out to the actual "internet". I suppose that in part that such platforms as Facebook is a regression to the earliest days of commercial electronic bulletin boards that were running before the internet itself permitted commercial sites, such old bulletin boards as Compuserve, AmericaOnLine (now the site AOL), etc.
So I have used the internet since around 1996, when I got my first dial-up modem. Gosh, those were awful! And the days before the "world wide web" and browsers. We had to use chat software (IRC), newsreaders for usenet, other programs for Archie - and Veronica (for some reason whenever I tried Archie I could only access a university in South Africa, weird). No web browsers back then.
But I met the woman who later became my wife on this early internet! On a usenet forum! That was not even for the purpose of such matchmaking! or socializing! It was a technical forum and we just clicked and went from there. We have been married for 20 years now.
So my experience with "social media" has been long standing, if perhaps not extensive...in the sense of using Facebook and now defunct sites such as Google+ and...gosh, now I can't recall the name of the old Microsoft platform.
So, what sites do I use, or used in the recent past?
They include:
LinkedIn - a networking site for professionals...or any working person. All related to working and jobs, all different businesses and industries. I maintained this while working. Now I have the same account but indicate I am retired, no longer associated with the software company. Apparently people don't read though as I continue to get contact requests from industry. I do maintain contact with some former co-workers, even 1 or 2 from many years ago (30+)
Eng-Tips - a site for all fields of engineering with discussion forums. I maintained an account under my real name (er, yes, Fred Smif is a pseudonym. oops) and had a reputation on there for ny work...presumably a good reputation. haha
Facebook - I have an account with a small number of "friends". I don't check in very often. I find it overwhelming with its broad array of uninteresting, unrelated chaff. I did use it last week or so to post a highly favorable review of a florist in another location I has just used. A number of my in-laws use Facebook heavily, I don't see how they have the timeto use it!
Google - well, there's no longer Google+ but even Google itself has some social aspects. So I participate to some extent in Google Maps...posting names of streets, etc, in oddball locations that I am familiar with, and a number of business reviews...including the florist mentioned above. But these are not very interactive.
YouTube - I love YouTube for watching/listening to music and some oddball things (live streaming street views of some cities I am familiar with) including my current passion, my daily dose of a video of Red Pandas from a Japanese zoo (I never realized just how CUTE these things are). I post comments on my favorite videos/music. But YouTube is not highly interactive
AARP forums - I am relatively active here. I try to read/post in a variety of forums.
Boglehead forum - an investment forum
MSN.com used to have a variety of forums, since closed for around 10 years, and I participated. Many have been moved to https://ymam.proboards.com/. I occasionally drop in.
city-data.com forums. A useful site for information on cities, etc, around the US (and elsewhere). Many forums on all different topics including those of interest to retirees.
And a number of other similar forums. So many!
er, I do maintain a nom de plume for each (except LinkedIn and Facebook). I actually maintain a spreadsheet of my login info for each (url, user name, password) to keep track of them all. Many people use such names so I don't feel particularly bad about it.
What do I get out of each forum? I look for information on topics of interest to me. I like to provide guidance to others (which was my work for those 20 years). And perhaps share my opinion and views.
Well, I guess I have rambled on more than long enough!