These names were originally masculine or gender neutral but nowadays they lean very feminine.
Or they were used historically for men too
Evelyn
Meredith
Avery
Mackenzie
Cassidy
Marion
Beverly
Darcy
Aubrey
Casey
Marley
Harper
Carol
Hilary
Kelsey
Ainsley
Lauren
Delaney
Courtney
Allison
Blair
Florence
Addison
Pearl
Vivian
Ruby
Harper
Shirley
Clare
Madison
These names are masculine in French, but happen to be feminine in English:
Lilian
Alexis
Esmé
Jules
Aimé
Lois
Maury
Jocelyn
Vivien
Jasmin
Camille (This in French is gender neutral, but by gender neutral I mean completely gender neutral - it has been popular almost at the same level of popularity for both sexes since centuries, sometimes leaning more masc and sometimes leaning more fem)
Élie
These names are masculine in Italian but feminine in English. They are all common names:
Elia (It is way more common for boys than girls. It is super rare for girls but not rare for boys. And it is pronounced for boys eh-LEE-ya, for girls EH-lya. They have different roots. For girls it is the feminine form of Elio. For boys the Italian form of Elijah)
Andrea (Though it has been used for girls too recently, not so rarely too, but still way more common for boys).
Gabriele
Nicola
Michele
I think that some word names can work for a boy too, in an ideal world:
Joy
Violet
Cedar
Sage
Opal
River
Wren
Lark (I always found this to have a masculine sound)
Leaf
Sparrow
Haven
Harlow
Marigold
Taiga
Moon
Hazel (I thought this name was masculine only, before I found out it was not. I am not from an English speaking country so I had no idea of the perception)
Lavender
Sorrell
Juniper
Kitty (As a name of an animal) / Kit
Vivendel
Hope
Scout
Some names that might sound feminine to English speakers
Vanya
Sasha
Isa
Sora
Yasha
Akira
Grisha
Borna
Still in an ideal world:
Heidi
Romy
Gertrude
Nova
Juno
Leonor
Ingrid
Alba
Millicent
Isabeau (since it ends in beau, a masculine suffix, and Isa is a masculine German name and does feel gender neutral to me)
Dagmar
Luna / Lune
Angharad
Clemence , Clemency
Iris
Hermione
Ingeborg
Adelheid
Tanya (If yes to Vanya, why not Tanya?)
Winifred
Artemis too. Was the name of a goddess. Demeter works too
I think Willow works better for a boy rather than a girl IMO.
Kiki works a gender neutral name for everyone. Where I live it is usually a nickname for Riccardo. I know a teen Riccardo who every call Kiki.
The only Jess (full name) I met was a boy from Taiwan.
More realistical choices in an English speaking country:
Remington
Bellamy / Bell
Artemis (As I stated before)
Quinn
Garnet
Sutton
Remy
Alexis (As I stated before)
Harper
Avery
Calle