Do we know much about any Forsaken or undead not raised by a Death Knight choosing to join the Ebon Blade? If you do not wish to be apart of the Horde or join the Argent Dawn would EB accept you? Or is there more emphasis on the KNIGHTS of the Ebon Blade + ex Lich King followers?
Edit:
Do they have living members?
Up until now the Ebon Blade are like a Police of the Undead Scourge. The story in-game so far is that they DID indeed expanded their ranks beyond the rebel DK that turn against the Lich king but they only expanded in the Fourth War to heroes who died honorably.
TL;DR: SO basically its an undead exclusive group dedicated to keep the scourge at bay.
I suspect if they somehow unify with the Forsaken and become some sort of Necropolis Nation I bet one of the first living members to join would be Nerubians… and maybe some special guess or support from the SL, like Gargoyles (Let’s face it SL Gargoyles are far superior than the ones DK summon or the Scourge control!) among others things or NPCs. (IMO)
There is at least one (1) lich among the Death Knights and one dude heavily implied to be a vampyr curse undead in some capacity (blood DK trainer)
In theory, there are more than just DKs in their ranks given the lich. Various necromancers at the very least.
This question does not have an answer in the canon
but one can speculate that some living are still drawn to necromancy and aspire to become a lich.
That would be me.
Ah, one of the classes ask since vanilla… Necromancer and Lich, diluted all into DK.
DK fan need to pray Blizz never add these classes, you know Blizz will just gut out DK skill just like they did with Warlocks when DH came out! 
With Necromancer I would take a different approach I make the Hero Class Lich… Necromancy would be part of my Specs specializing in Corpses synergy and summoning like Necromancers in ESO and GW2 maybe even healing?
Second spec Would be theme after Nerubian and Domination Shadow Magic taking lore from the “Trands of Fate that Binds us” and expand it into a different powers to CC, poison, drain health or other resources from the living and different types of pestilence looking spell like the Nerubian would use.
The Third Spec would focus on Flesh Craft and Runecarving mix of Buff and de-buffing Like Augmentation but… as you Augment or Buff your Allies you automatically debuff or Drain your enemies giving them a negative de-buff or something like that.
So that they don’t touch the DKs skills… no clue on what a Lich Hero Spec (Maybe add Slime or Fungi like DnD druids who follow the Circle of Spores? Although I think this fits into Normal Necromancy) would look like… though.
They could just add a class skin for warlocks
Demonology with Diabolist already plays how Necro would play
Just add a glyph where all the demons become undead, an dall the fire/fel abilities become shadow/blue
Voila
Oh yeah this could actually work… I wonder why they never did this? Seems like a win win.
Class skins are a long time ask
Blizzard just disagrees
problem is you are trying to understand undead lore
you need to turn your brain off like with how time travel works
undead lore is a huge meme which includes such gems as the crazed phase
The ebon blade stole our whole flow bar for bar.
Not all of it.
Forsaken had exactly one single moment where they were a standing army.
But yeah it sucks to not see the forsaken do anything.
I remember in Shadowlands, there are DK units that don’t have the eyes. As if they are living people among the DK ranks.
I found it curious, so I posted about it.
The consensus from people who replied was that they were probably supposed to be regular dead DKs that didn’t get the proper attention during development.
Edit for clarification:
I am talking about the Horde NPCs in Oribos that maintain the Org portal. They aren’t wearing helmets. They have DK voice lines, but they don’t have the Blue Eyes - they have normal eyes, as if they are alive.
The Alliance NPCs have helmets on, so it’s hard to tell.
Probably just an over sight more than acknowledgement of living members being part of the Ebon Blade.
Shadowlands showed them to have mages among their ranks, as there are Ebon Blade personnel maintaining the Oribos portals as regular arcane portals, not death gates.
The Alliance ones don’t have the glowing DK eyes either, though the human one uses the cultist face markings and might use one of the DK skin textures. Lots of DK npcs use the cultist markings without the glowing blue eyes while still definitely being DKs (Thassarian, Thorval, Whitemane), so lack of blue eye glow isn’t a sure way to determine if those mage NPCs are undead or not. If they’ve got the voice echo, they’re probably meant to be undead.
Honestly at this stage the Forsaken are a joke. lol