I played once with hosting a VSCode server on a raspberry pi for general development and it was actually quite powerful, when used from an iPad. Just not strictly for Swift unfortunately
The ecosystem is fine for non-Apple development. It's just building apps for iOS, macOS, etc. that is impossible on iPad right now past some basic applications.
I'm hosting a VSCode server with Termux/Ubuntu container on my old Pixel 6a and I cannot overstate how awesome it is for just a fun dev setup, especially with a tablet. Easy to nuke and start clean too!