iOS has provided a glyph for ⏻ U+23FB POWER SYMBOL since iOS 14:

https://tofu.quest/?q=%E2%8F%BB

(Full disclosure: I maintain a project that catalogs which Unicode codepoints are covered by the default fonts on iOS and Android ( https://github.com/amake/CodePointCoverage/ ); this feeds tofu.quest which is also my project.)