Twitter: not a bad place to establish a way for people to find out what's going on with your company, or a simple way to contact you for customer service or something like that.
Discord: can be useful if your company gets big enough to have a community(see Corsair, XLR8, NZXT, etc). Not much use outside of that, though.
Pinterest: there can be professional presence here, but probably not for your field.
Instagram: similar use case as Twitter.
Reddit: for a company, not really much reason to invest in it.