I'm playing a barbarian in BG1Tutu. Since they can't wear heavier than splint mail, what's the best armor for them?

Can they wear Ankheg armor (if so, that'd probably be the best)?

Ankheg armour is classed as plate armour so Barb shouldn't be able to wear it.

There is magical splint mail in the Ankheg burrow on the BG city bridge map.

Not sure what other splint/chain is available in Tutu. In BG2 the best would probably be Drow Adamantine chain but that won't come until fairly late in the game.

I found out there's a set of Chain +3 deep into Durlag's Tower, which would be really tough for a solo Barbarian to get.

The best armor, IMHO, is a suit of regular Splint Mail while wearing a ring or cloak of Protection +2.

This might be a bug or exploit, but I managed to keep a suit of Plate Mail (_iplat01) I swiped off Canderous (an NPC who joins when you fight the illusionary monsters in Obe's house). It doesn't have the not usable by Barbarian flag set.

But the best armour you could possibly get for a barbarian is the Mithril Chain Mail +4 from Drizzt (see my other reply to yours just posted for strategies for getting that).