Not all fonts have Unicode character ☰ [WayBack] Unicode Character ‘TRIGRAM FOR HEAVEN’ (U+2630) as it is in a less common block.
More fonts have Unicode character ≡ [WayBack] Unicode Character ‘IDENTICAL TO’ (U+2261)
The latter is slightly shorter and slightly narrower than the former, but works in way more places.
Via [WayBack] html – Unicode ☰ hamburger not displaying in Android & Chrome – Stack Overflow
I’ve worked around this problem by using the UNICODE character UNICODE U+2261 (8801), ≡ IDENTICAL TO as illustrated below rather than the UNICODE U+2630 (9776) ☰ TRIGRAM FOR HEAVEN which
–jeroen