Imagine uploading was added so very long ago. It makes me think that you aren't on the latest version? This is the latest version. Can you confirm? 
Discussion
oh wow I'm not updated I guess. but I'm not seeing how to update on Google play. no update prompt ...
Just do not use google play for that. You can install Obtanium, add the Primal official github repository and Obtanium will detect an update every time a new Primal release build is available. Same for all the other open source apps...why use Google Play for installing OSS apps?
This is all new to me mate. Where do I install Obtanium?
Here you have the official website https://obtainium.imranr.dev/
Just do not use google play for that. You can install Obtanium, add the Primal official github repository and Obtanium will detect an update every time a new Primal release build is available. Same for all the other open source apps...why use Google Play for installing OSS apps?