The first stable version with the new API was released almost 2 years ago. I have myself ported a vte-based terminal emulator (whose codebase I was not familiar with), it took maybe like 2-3 hours, can't remember, but definitely not much more.

The problem is that for some reason we `dlopen()` VTE, and 0.38 lacks runtime version checking, so it's harder than it should. But yeah maybe we could play and assume it's 0.38 if an older symbol is missing and a newer present (although it's made even more annoying to do than it should because the [0.38 docs](https://developer.gnome.org/vte/0.38/) lacks any "new in 0.38" docs, so it has to be guessed). It'd probably be doable, but VTe really doesn't help here.

(I don't think parallel support for 2.90 and 2.91 makes any sense, just go for 2.91 and forget 2.90 for good).

No. Unless there's a compelling reason to drop 2.90, we should not drop it.

A note about `vte_terminal_set_background_image_file()`: Indeed direct support for background image has been removed; however, see the Terminix project how a picture can be drawn behind a transparent/translucent VTE using some GTK+ magic.

Probably makes sense. But well, it's a retarded feature anyway, so why bother.