Can You Install Adobe Flash on Nintendo DSi XL? No
Impossible. The DSi XL runs a proprietary Nintendo OS on ARM7/ARM9 CPUs. Adobe Flash Player was never ported to this architecture, and the hardware lacks:
Sufficient RAM (16MB) / CPU speed for Flash runtime.
Browser plugin architecture (DSi Browser is a stripped Opera, no plugin support).
Video decode acceleration for Flash video.
Alternatives
DSiWare / Homebrew: Some homebrew apps (via Memory Pit / Flipnote exploits) play specific video formats (DPG, M4V) converted on PC.
PC Emulation:melonDS, DeSmuME run DS games + browser (with Flash) on PC.
Modern Device: Phone/tablet/PC for any Flash content (via Ruffle emulator or archived SWF).
