How long should you immerse meat in a baking soda solution to achieve maximum tenderness?

Baking soda?? Never heard of that!
Usually, a slightly acidic solution is used to tenderize meat before cooking, like tomato sauce. (Be sure to discard tomato sauce and other solutions after using to tenderize, lest someone gets sick from salmonella.)
Overnight in the fridge is good.

Please explain the logic . . . .

Baking soda works for crispy chicken skins . . .! ! !

I’ve not heard of that either.

The tender meat technique I know involves a slow-cooker, salt and water.

Longer isn’t better. The soda needs to penetrate the meat to create the desired chemical reaction, but won’t continue its effect forever. Once the meat has reacted, it is ready.

Overly simplistic guidelines:

Baking soda dry rub (don’t use a solution. Water will replace meat juices, stealing flavor.)

Thin cuts – ½ hour
Thick cuts – 3 hours
Roasts – overnight

It doesn’t have to be much baking soda and it doesn’t have to “marinate” for too long. Here is a good explanation of how much to use and how long to let it sit and how it works.

I am not a fan of a velveting with baking soda. I prefer it with cornstarch.
It will tenderize tough cuts of meat in about 15–30 minutes. ½ teaspoon of diluted backing soda to ½ pound of meat.
The key is to rinse it THOROUGHLY after you are done. This will remove the chemical/metallic flavor that could result in not rinsing.
Now marinate of your choice of flavoring.

Vinegar is the ticket for me; not baking soda. When I do it, I leave the meat in the vinegar for a couple of hours in the refrigerator. If I’m going to cook pork ribs in the oven, I put the ribs in a dish that will accommodate vinegar half as deep as the ribs are tall. I cook covered for an hour or so then turn them and cook some more. At that point I put the ribs in a clean dish and season or add sauce and bake a while longer uncovered.

I’d heard of velveting chicken to moisturize it and marinating beef, but never using baking soda. However, here’s an article about velveting beef with either baking soda or cornstarch. Hope it helps.