Pi-hole is described as 'Protect all network devices with DNS-level ad blocking, no client software needed. Features a web interface, query logging, whitelist/blacklist, and privacy controls' and is a very popular Ad Blocker in the web browsers category. There are more than 25 alternatives to Pi-hole for a variety of platforms, including Linux, Windows, Mac, Android and iPhone apps. The best Pi-hole alternative is Portmaster, which is both free and Open Source. Other great apps like Pi-hole are AdGuard, NextDNS, simplewall and RethinkDNS.
Portmaster is a (great) local firewall, pi-hole is a dns-blackhole. Not an alternative in the slightest though.