I expect that Ardling will (and should) return in a supplement.  It's not something that I think belongs in a core rulebook.  I'd disagree with Tieflings being there too (and I really like tieflings), if it weren't for their popularity.  That popularity though is key.  Core rulebooks should have options that appeal to the widest variety of players, because the widest variety of players will have those books.  Niche content should be avoided and saved for those non-core supplements.  Aasimar never enjoyed the same kind of popularity that tieflings did for a few reasons.  One, imo, they were mechanically weaker.  Two, they didn't have the lower planar edginess that the tieflings have to offer for our edgelords out there.  Ardling is a furry aasimar.  It brought nothing to the table that Aasimar didn't except the fursona that is a massive turn off to a lot of people.

So, it along with Aasimar (which I have always liked going back to 2e) do not belong in a core rulebook.  Just because I like something, does not mean it belongs in a core rulebook.  The same applies to niche content that YOU may like.  Just because you like it doesn't mean that this is the proper book for it to be in.

My fix: go mundane, and leave the extra-planar nature to either species feats and/or the new mixed-species rules (crossed with aasimar).

Beastfolk (Mundane Ardling)

Creature Type: Humanoid
Size: Medium (4-7 feet tall) or Small (3-4 feet tall), chosen when you select this species.
Speed: 30 feet
Life Span: 100 years

• Animal Ancestry
• Climber
• You have a Climb speed equal to your Speed.
• Once per turn when you deal damage to a target with your Unarmed Strikes, you can increase your damage to that target by an amount equal to your Proficiency Bonus.
• Defender
• You have an extra thick hide or protective scales.
• When you aren’t wearing armor, your base AC is: 13 + Dex bonus.
• When you are wearing armor, you have a +1 AC bonus.
• Flyer
• You have wings or winglets that are of minimal utility.  They can be feathered wings like a bird, leathery skin wings like e bat, or even loose skin areas under your arms.
• When you take the Jump action, you have advantage on that action’s Ability check.
• When you fall from at least 10 feet height, you may use your reaction to glide downward, taking no damage from the fall.
• Racer
• You are built for sprinting.
• You may take the Dash action as a Bonus Action.
• Your Speed increases by 5 feet (35 feet total).  It increases by another 5 feet at each of the following levels: 5 (40 total), 11 (45 total), 17 (50 total).
• Swimmer
• You can hold your breath for up to an hour at a time.
• You have a swim speed equal to your Speed.
• You have resistance to Cold damage.
• Primal Senses
• You have Darkvision 60 feet.
• You have advantage on any ability check that would involve knowing compass directions (knowing which way is north, knowing which compass direction a path goes, etc.).  This includes any form of navigation.
• Nature Affinity
• Choose Proficiency in one of the following skills:
• Nature, Perception, Survival

Species Feat ideas:

Any:

• Ardling: you have a connection to divine or primal magic.  Pick the Cleric or Druidic spell list when you take this Feat.  Each time you finish a long rest, you may prepare one cantrip from that spell list, which does not count against your number of known/prepared cantrips. (probably needs a little more than this, to be as interesting/useful as Magic Initiate)
• Echolocation: you have Blindsight 30 feet and are immune to being blinded, but being deafened, or being within a radius of silence, nullifies this feature for as long as the deafness/silence affects you.
• Prehensile Tail: (can’t wield a weapon nor perform somatic components, but can wield a shield or hold other objects) (if it’s not holding anything it can be used to make a bonus action unarmed strike, or for advantage on checks involving balance or keeping a hold on something)
• Primal Warrior: you have claws, spines, talons, fangs, horns, a beak, and/or a swift strong tail that are useful for making Unarmed Strikes.  Your Unarmed Strikes damage is 1d6 + your Strength modifier.
• Multiple Features: some animal types might have the features of several Animal Ancestries, such as a Hippopotamus who has both a Defender’s thick hide and being an excellent swimmer.  Another example might be an Ostrich as a Racer who has the secondary traits of a Flyer.   Taking this feat lets you add a second Animal Ancestry feature.  (should there be any restrictions what you can combine?  maybe this one can only be taken once)
• ?  Burrower?  add a burrowing speed and an ability to hold breath?

Climber:

Defender:

Flyer:

• Identical to the Draconic Wings feat, changing your wings from semi-useful to fully useful.

Racer:

• A feat comparable to Charger, but more specific to Beastfolk?

Swimmer:

• ?  Gills and increased swim speed?

Also, a celestial beastfolk could easily have their celestial nature be a _Background_ , picking up the Magic Initiate Feat and Celestial language.  And if you really want to, add a background-based spell list (like the Strixhaven backgrounds have).

Quote from johnkzin >>

Also, a celestial beastfolk could easily have their celestial nature be a _Background_ , picking up the Magic Initiate Feat and Celestial language.  And if you really want to, add a background-based spell list (like the Strixhaven backgrounds have).

Background:  Extraplanar Upbringing

You grew up on a plane that isn’t part of the Material Plane.  Possibly an upper plane, lower plane, neutral plane, or even an elemental  plane.

Attributes:  +1 INT, +1 CHA, +1 WIS
Languages: Pick a language that matches your plane (Celestial, Infernal, Abyssal, Primordial, etc.).
Skill Proficiencies: Pick two from: Arcana, Nature, Religion
Tool Proficiencies: pick one Musical Instrument
Feat:

• Magic Initiate (Cleric or Druid)

Bonus Spells: (optional, depending on Campaign’s power level)

Depending on your planar association, you know either the Elementalism cantrip, or the Thaumaturgy cantrip.

You always have these spells prepared, once any of your classes are able to cast spells of the given spell level.  They do not count against your number of spells known/prepared from any of your classes.

• 1st Level Spells: Protection from Evil and Good, Sanctuary
• 2nd Level Spells: Augury, Gentle Repose
• 3rd Level Spells: Magic Circle, Tongues
• 4th Level Spells: Banishment
• 5th Level Spells: Contact Other Plane, Dispel Evil and Good
• Depending on your planar relationship, you also know one of the following spells when you are able to cast spells of that level:
• One of: Summon Celestial, Summon Elemental, or Summon Fiend