Notes and disclaimers: this requires a device with more than 4 gigabytes of ram, it can be done with devices with lower amounts, but can lead to crashes and errors of all shapes and sizes, also, all 1.9+ parts and techniques will not work, such as funky trees and cannons. (Your phone will get hot during this, not damagingly hot though, unless your doing processor heavy stuff for long times)

Step 1: install VMOS from the play store.
VMOS is a virtual machine for android, coming with android 5.1.1 out of the box

Step 2: aquire a copy of simpleplanes version 1.8.x, this will be imported into vmos

Step 3: install a file explorer, this will be imported into vmos

Step 4: activate vmos and navigate to the import tool (the file folder thingy) and import your simpleplanes apk and your file explorer into vmos (don't worry, it's super simple to do, anyone could figure it out)

Step 5: open up your file explorer and install simpleplanes using it, then go to the inbuilt browser and get the upload with screenshots mod, and install it like usual (the play store inside vmos is broken so you can't get chrome)

Step 6: import your airplane file, or back it up online and download it using the browser.

Step 7: take your screenshots and upload!

More notes: if you didn't figure it out already, use the widget to navigate around vmos, since the bottom buttons are really finicky. Also, if your phone supports PIP (android 7 and up usually does) you can run vmos in a little window on top of your normal operating system, so you can grind a mobile game while playing simpleplanes or watching YouTube. It even works when minimized. (I think)