For those who are interested in the Tortle race, it can mostly be added via the custom page. It is considered part of Xanathar's Guide to Everything and is legal to use in the Adventurer's League. The armor and the Unarmed strike (claw) can be handled via with Start page. The Unarmed strike (claw) needs overrides to give the character proficiency and change the damage to ="1d4+"&STRMod. For the armor, set the armor to Mage Armor and then set the overrides like this pic.
Name: Tortle
Size: Medium
Speed: 30
Skills: 1 Survival
Languages: 2 Common, Aquan
Height: 4'10"+2d8
Weight: 400x1d6 (The Tortle Package sets the height as between 5 feet and 6 feet, and the weight as an average of 450 pounds.)
Ability Score Increments: +2 Strength, +1 Wisdom
Age: Young tortles crawl for a few weeks after birth before learning to walk on two legs. They reach adulthood by the age of 15 and live an average of 50 years.
Trait 1: Claws. Your claws are natural weapons, which you can use to make unarmed strikes. If you hit with them, you deal slashing damage equal to 1d4 + your Strength modifier, instead of the bludgeoning damage normal for an unarmed strike.
Trait 2: Hold Breath. You can hold your breath for up to 1 hour at a time. Tortles aren't natural swimmers, but they can remain underwater for some time before neededing to come up for air.
Trait 3: Natural Armor. Due to your shell and the shape of your body, you are ill-suited to wearing armor. Your shell provides ample protection, however; it gives you a base AC of 17 (your Dexterity modifier doesn't affect this number). You gain no benefit from wearing armor, but if you are using a shield, you can apply the shield's bonus as normal.
Trait 4: Shell Defense. You can withdraw into your shell as an action. Until you emerge, you gain a +4 bonus to AC, and you have advantage on Strength and Constitution saving throws. While in your shell, you are prone, your speed is 0 and can't increase, you have disadvantage on Dexterity saving throws, you can't take a reaction, and the only action you can take is a bonus action to emerge from your shell.
Trait 5: Survival Instinct. You gain proficiency in the Survival skill. Tortles have finely honed survival instincts.
Armor Class, Base: 17
They prefer to be Lawful, and mostly good, though Lawful Neutral and even Lawful Evil are not unheard of.
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I have read some opinions about a Tortle's dexterity being a dump stat because it does not affect a Tortle's AC, but I disagree. Their dexterity score still affects everything it normally affects, except armor class. The Tortle's natural armor is effectively Heavy armor, without the strength requirement, no stealth disadvantage, and any class can use it with proficiency. You can even sleep in it, eliminating those pesky Don/Doff delays. A downside is that it can not be enchanted (subject to a DM or WotC ruling otherwise), and you can't swap it out for better armor (plate mail).