Extension no longer installable by composer – do it manually?

I am upgrading a dev site to 2.4.5. One of the third party extensions , when I tried to update via composer it didn’t work. Couldnt’ find anything on their website so emailed them. I got the following back:

“The solution is no longer in active development so the installation using Composer is no longer working properly. With that said, you can perform a manual install by extracting the files into your Magento environment instead.”

In the live production site the extension is in vendor. Should I be able to just copy that over to the new site, pop it into vendor and run magento upgrade? Or should I copy it into app/code? I have emailed back but just wondering in the meantime…

Thanks