You should check out Procreate. For me, it alone is enough reason to get an iPad.
You can side load it using a developer account without jailbreaking.
Seems like with iOS 14+, and as of writing it seems like we're on iOS 17, it needs to be jailbroken? Do Jitterbug, Jitstreamer, AltJIT, work for developer accounts?
Adobe shipped Photoshop for iPad in 2019: https://www.adobe.com/products/photoshop/ipad.html
GIMP for iPad: https://apps.apple.com/gb/app/xgimp-image-editor-paint-tool/...