This blog, dated July 2019, says California items and digital services are not taxable, which would cover the XBox Live 12-month subscription gift card I bought.
https://blog.taxjar.com/sales-tax-digital-products/
While eBay is claiming they are going by an "October 2019 law", they're referring to the necessity to collect tax on merchandise sold online regardless of where the seller is located, NOT to start charging tax on digital items.
BTW, that gift card was transferred to me electronically. I did not receive any physical item.