Walking around wearing Meta’s hardware supports them by you advertising their product (unless you never show anyone that you own the hardware).
The existence of a used market also slightly increases the value of new things. By buying used, you’re supporting/signaling the used market and indirectly supporting the company.
If you don’t want to support a company, don’t go near their products.
“Advertising the product” is an extremely mild form of support in this case.
Your criticism of buying used is complete nonsense. Secondary markets have put companies out of business. You’re not “signaling” anything except that the price is too high.
You are right, it's double-edged. In some cases it can hurt companies (e.g. luxury good companies) while in other cases it can benefit them (e.g. car companies benefit from the second-hand market in many ways). It's a fascinating economics+psychology topic.