What will be the last macOS upgrade for the 2019 Intel Mac Pro ?

Apple's supported/non-supported criteria are laid out in this support page:

Obtaining service for your Apple product after an expired warranty - Apple Support

Note that the criteria can vary by locations due to variations local consumer protection laws and regulations.

Also the article reenforces a key factor that Grant mentions: end of support is based on when Apple STOPPED distributing them for sale, not the year of introduction. Using that criteria, yours is "vintage" after 2028 depending on where you are.

That Mac Pro model was discontinued in 2023, and the first one was running MacOS 10.15.1, Catalina. It can run the current MacOS.

2019 Intel Mac Pro

2019 Intel Mac Pro

na-el25 wrote:

2019 Intel Mac Pro

So what Exactly is your QUESTiON?