First of all: a 3b account is only deductible in Geneva (CHF 2’200.-) and in Fribourg (CHF 1’000.-).
Second of all: don’t get a 3b.
That’s it for the advice.
Now some explanation: a 3b account is everything that you can consider a saving. For exemple, your saving account, an investment fund account (Targeted saving and investing | UBS Switzerland), an investement solution like Selma, Truewealth, CleverCircle, or a private broker (Swissquote, DeGiro, Interative Brokers).
However, theses providers can’t be deductible because the only way to deduct a 3b is by having a shitty 3b life/disability-insurance, the one which is like the shitty 3a life/disability-insurance 