Zend certified PHP/Magento developer

Open source tools to make equirectangular to/from Cubemap conversions

My goal is to be able to digitally design a 360 image using free software.

I’ve found this tutorial, but it includes the use of Photoshop and therefore Flexify 2.
https://studiobehind90.com/how-to-create-360-panorama-painting-in-photoshop/

Does anyone know of a workaround?
– possible combos:
software to replace Flexify 2 plugin using photopea
alternative to photopea that allows a Flexify 2 replacement.