I've had the Poetic tempered glass on my V40 for 3 months with no problems. It sticks fine and has no halo or rainbow effect. Some reviewers have reported issues so ymmv, but for the price, I'd definitely give it a try.

https://www.amazon.com/gp/aw/d/B07HNNBJLC/ref=oh_aui_i_d_old_o0_img?ie=UTF8&psc=1

I personally like the screen protectors with the black borders around the edge.

LG V40 Screen Protector, Poetic [HD Clear][Anti-Fingerprint] Premium Tempered Glass Screen Protector for LG V40 (2018) - Clear/Black https://www.amazon.com/dp/B07HNNBJLC/ref=cm_sw_r_cp_apa_i_Xu.QCbRG94WHY

The poetic fell off of my phone after one hard drop on a hardwood floor. Adhesive is poor. Great protector no rainbow effect.

SEEU LG V40 ThinQ Glass Screen Protector-(3 Pack) Anti-Fingerprint Anti-Scratch Ultra-Thin HD Clear 9H Hardness Full Coverage Silk Print Black Tempered Protective Film for LG V40 / V40 ThinQ 6.4" https://www.amazon.com/dp/B07HQLXKDR/ref=cm_sw_r_cp_apa_i_qx.QCbNJD9VRX

I bought the seeu protectors next. You get three in the package. The adhesive is much better. These protectors are very reflective which I don't like. There is a small rainbow effect down the middle but it doesn't bother me.