I use a bit of CSS to mark articles from domains that use a paywall with a red dollar sign. (Assuming you know how to add CSS to pages...)
/* paywall domains */
a[href^="https://www.economist.com/"]::after,
a[href^="https://www.ft.com/"]::after,
a[href^="https://www.newscientist.com/"]::after,
a[href^="https://www.telegraph.co.uk/"]::after,
a[href^="https://www.thetimes.co.uk/"]::after,
a[href^="https://www.wsj.com/"]::after {
color: rgba(128,0,0,0.75) !important;
content: " $ " !important;
}
