Yeah I'ma just. Doubt that one significantly. I know Bladesinger is an uncannily good tank but, you can't draw a tank out of every class.
Clerics in Heavy Armor and Druids are born to tank.
Warlocks go Hexblade, max strength and Constitution, Variant Human and start with heavy armor proficiency, Heavy Armor Master at 4th level. Armor of Agathys, then Blur at 3rd level, Shadow of Moil art 7th. Pick up Feindish Vigor and Tomb of Levistus as an Invocations.
Rogues play Arcane Trickster, get Medium Armor through a Race then pick up heavy armor or alternatively medium armor master through a feat at 4th level. You can do this either with a dex build or a stength build. If you do it dex you probably want to start as Variant Human or Custom so you have shield proficiency.
Sorcerer you play a Mountain Dwarf, Divine soul. Max strength, Con and 14 Dex, Greatsword or Maul. Heavy Armor at level 4, Heavy Armor Master at level 8. Shield spell and Shield of Faith, false life, absorb elements. You aren't using a shield in this build but your AC is still plenty high and you have a bag of hit points because you are using highest level slots on false life.
Bard is really the most difficult, but it is doable even there. Start Variant Human or Custom with Medium Armor and shield. Go Valor Bard. This is really the weakest and this character by using spell slots for healing word as a bonus action. You are also going to leverage the combination of Defensive Flourish and Silvery Barbs.
To tank, those casters are going to run a low casting stat and they are going to use spells for defensive options, temp hit points or healing, but they are all workable as a tank.
Plus, with healer out? The only roles left are... DPS and tank, which, yeah, the other classes are doing, but not well
Face, explorer, tricks/traps, exploration, ranged .....
If we're using "Can't be a tank" to exclude classes then we'd be kicking the rogue out of the game
Rogue is doable as a tank. There are actually two ways to do it on point buy:
1. Mountain Dwarf. S17 D10 C17 I14 Level 4 Heavily Armored, Level 8 Heavy Armor Master, Level 10 ASI (20 STR/18Con), Level 12 Tough ... Arcane Trickster for Blade cantrips, shield, blur - AC 18 (23 with shield), HAM and uncanny dodge to reduce damage
2. Variant Human-Moderately Armored. S10 D17 C16 I14 Level 4 Medium Armor Master, level 8 tough, level 10 Con ASI, Level 12 Con ASI. Arcane Trickster for blade cantrips, PEG, Blur. AC 20, uncanny dodge to reduce damage
With cunning action dash I think either of these Rogues will tank better than most Barbarians at most levels.