is there an effective lvl 20 dodge tank build? High mobility/ AC, high aggro, high hit count Tank build

18 monk 2 Barbarian? Mobile feat? Monk with rage that can avoid opportunity attacks? 18 Barbarian 2 rogue? Barbarian with bonus action disengage and tough feat. I dunno I don’t have a lot of experience with level 20, just some ideas off the top of my head.

Homebrew Wizard  with rolled stats (or point buy, whichever is higher)

Paladin has a spell called compelled duel.  Basically, it's taunt.

There are several cleric spells that help, such as Shield of Faith and Warding Bond that they can cast on the Paladin, helping him out.

Makes for a good paladin tank build

D&D doesn't have a concept of "aggro". There's one or two features or spells that might force or discourage an opponent from attack someone or force them to attack you, but they're relatively rare. For the most part, the weak characters stay out of the way or the group uses abilities to mitigate harm against them.

Any Paladin oath, the Path of the Ancestral Guardian Barbarian and the Cavalier Fighter can all achieve high AC and have tools to keep other characters safe. Also see the Sentinel and Mobile feats.

I have a ranger with magic armor It's only medium but it's(AC 24)

Dwarf barb/monk w dwarf race feat: reckless attack, burn 1 ki to dodge as bonus action=heal in combat & neutralize reckless attack drawback.

elven bladesinger with rogue dip or vice versa 20 dex and 20 intelligence equal 20 ac without armor or 28 wirh mage armour and shield spell