Can Ekko still build tank?

Yes

The four builds for ekko that are all viable

1-Tank Ekko You obviously know it

2-AP ekko You obviously know it

3-Off Tank Ekko Items like ROD and Rylias that give you ap and health

4-Bruiser AP ekko Half AP half Tank

You can even play him ad if you want (don't actually try it in ranked -.-) it's just AS build for fun :D And yes you can still build him as a tank but a bruiser build with 2-3 ap items is still better than a full tank Ekko

The best Ekko build here for me personally and the best on the game.

I sometimes will even swap out and sell my boots if its a close game cause at that point, its all team fighting, and well, the more armor or MR, the better, so go and sell your boots at the very late game.

He's my favorite champion, and I do beast with him so yeah. I've tried tons of builds, this is the best one. Also, Tank Ekko has the better chance of surviving and getting off his AOE stun from W. Usually you gotta dash in and get blown up, but tank Ekko will live, and create opportunities.