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The best approach is to only attend the chapels of organizations that ensure the validity of the priests they allow to operate in their chapels. That's basically how it worked before Vatican 2. The bishop of each diocese would only allow priests that he approved of and was certain of their validity to use his chapels.
Today, you could just check out the organization that operates the chapel you want to attend, and ask them what their policies are for determining who they allow to function as a priest. If they only allow priests with an unbroken line of traditional holy orders to function in their chapels, then you can safely attend all their chapels without concern.
Which organization(s) do you trust and why?