Topaz Labs makes a stand-alone upscaling app with proprietary models, or you can use something like Cupscale and try various models that are freely available. You usually need to chain multiple models together with the latter option in order to get decent results.
Edit: here are some links to get started…
Cupscale - https://github.com/DrPleaseRespect/cupscale/releases
Models - https://nmkd.de/?esrgan
More models & info - https://upscale.wiki/wiki/Main_Page