iPadOS is increasingly powerful - however, as you observe, this platform doesn’t yet have a broad choice of code compilers.
However, iPadOS does support Swift - and does have Swift compiler App:
Swift - Apple
Swift Playgrounds - Apple
https://apps.apple.com/gb/app/swift-playgrounds/id908519492
Don’t be fooled by the App - that teaches coding from first principles. While Swift is easier to compile using a Mac computer, the Swift Playgrounds App can reportedly be used to develop serious projects.
Apple does invite submission of comments and feature requests via its Product Feedback portal. If you would like to see other compiler support in future versions of iPadOS, this would be the most appropriate to communicate your request to Apple:
Feedback - iPad - Apple