For those that don't know about it, here are some links for FREE digital comics.
Free Digital Comics - Marvel Comics - New titles are added typically each Tuesday. Most books rotate out after 2 weeks. Marvel does have a few recurring freebies.
Free Digital Comics - DC Entertainment - Less frequently added books, but most books remain free once they are offered as such.
Free Digital Comics - Comics by comiXology - New titles added each week. Various publishers.
https://digital.darkhorse.com/free/ - Looks to be a static list once books are added. Mostly licensed titles.