Paywall
A paywall is a method of restricting access to content via a paid subscription. Beginning in the mid-2010s, newspapers started implementing paywalls on their websites as a way to increase revenue after years of decline in paid print readership and advertising revenue. In academics, research papers are often subject to a paywall and are available via academic libraries that subscribe.
Firewalld
Firewalld currently does not support outbound rules to the same capacity of inbound rules. Limitations include things such on ipsets, service names, and default outbound block by default rules required by standards such as NIST 800-171 and 800-53. Default block all needs to be done at the "raw" IPTables level via the --direct flag, and with the order of operations FirewallD uses to prioritize Rrules, rich rules, direct rules, it may be easier to enter all rules for outbound via --direct or use iptables (netfilter-persist)