

You can’t directly convert the app to make it natively android; android is too different for that. The app is built to use the whole android OS, not just the kernel (which is forked from linux). That means the android app is designed to run on mobile processors (usually ARM), and will be making calls to the android OS for everything.
You can’t repackage it directly as a linux app. However there are emulators and translation layers that cannbebused to run android apps within linux.
Waydroid for example allows android apps to run using android containers in linux. Anbox is also a container approach to running android apps. Both these approaches essentially translate for the android apps, and reduce the overhead asnthey dont have to emulate everything and can directly pass instruction to the linux host system. You can also use full virtualization to emulate an android device and run a whole virtual device. This would have a bit more overhead though.
I’m not aware of tools that can be used to compile android apps from source in to linux apps. It could be done in theory but would be complex due to the degree of translation of android APIs needed. Again compiling into some kind of container approach (I. E. Compile to include anbox or waydroid) might be doable but would bloat the app. I dont think there is the demand for that kink of approach when building in containers into Linux (and Windows) allows direct reuse of the android apks.
Not sure that is true? On a quick search, in the UK 3 in 10 had used it for point of sale purchases and 8 in 10 had used it online in 2023-2024. Of course that is used it at least once and does not reflect its actual market share.
https://www.statista.com/statistics/1389396/paypal-adoption-in-uk/