APL (Dyalog Unicode), 44 bytes
thanks @Adám for the ⍸⍣¯1
trick
(⊂a)∊(⍉¨⊢,⌽¨)⍣2≥∘i¨⍳⌈/,i←⌊/↑⍳⍴a←⍸⍣¯1(⊢-⌊/)⍸⎕
⍸⍣¯1(⊢-⌊/)⍸
trim surrounding 0s
≥∘i¨⍳⌈/,i←⌊/↑⍳⍴a
generate L-shapes
(⍉¨⊢,⌽¨)⍣2
add reflections
(⊂a)∊
test if the (trimmed) input is among them