All 3 Uses

however
in
The Maze Runner
(Edited)

Any pity Thomas had felt for Gally, however remote, completely vanished at that statement.
p. 159.3

however = regardless of how
He felt the slightest hint of peace, as fleeting as it was, and tried to enjoy it for however long it might last.
p. 319.9 *

however long = whatever length of time
However, if there was one thing his gut told him, it was not to admit to any doubt.
p. 322.3 *

however = though (used to connect contrasting ideas)

Definitions:

(1) (however as in: However, complications may...)
though (or another expression that connects contrasting ideas)

Based on idea 1 we might not expect idea 2, but this is a way of saying that even though idea 1 exists, we still have idea 2. Synonyms include in spite of that, despite that, nevertheless, nonetheless, on the other hand, in contrast and but.
(2) (however as in: However much she tried...)
to whatever degree (regardless of how much; or whatever unspecified amount)
(3) (however as in: However you do it, get it done!)
in whatever way
(4) (meaning too rare to warrant focus)
Much more rarely (and arguably incorrectly), however can be used to intensify the word how, as when one says "However did you find her?" Grammarians would suggest using two words for that usage: "How ever did you find her?"