24 games ranked by how much the tags Steam players vote on them overlap with Popup Dungeon's. A rare tag counts for far more than one that sits on half the store, and popularity never moves a game up.
What they share most: Turn-Based Tactics, Dungeon Crawler, Turn-Based, Turn-Based Strategy, Rogue-like, Rogue-lite.

1·The Dungeon Of Naheulbeuk: The Amulet Of Chaos
85% match · Turn-Based Tactics, Dungeon Crawler
87% of 8,103 reviews positive

2·Dungeon Rushers
85% match · Dungeon Crawler, Rogue-like
62% of 1,235 reviews positive

3·Dimensionals
85% match · Turn-Based Tactics, Dungeon Crawler
80% of 530 reviews positive

4·Wildermyth
85% match · Party-Based RPG, Tactical RPG
95% of 18,291 reviews positive

5·Age of Fear: The Free World
84% match · Tabletop, Tactical RPG
83% of 410 reviews positive

6·Heroes of Steel RPG
84% match · Dungeon Crawler, Party-Based RPG
78% of 286 reviews positive

7·Super Dungeon Tactics
83% match · Turn-Based Tactics, Tabletop
78% of 148 reviews positive

8·Tenebris: Terra Incognita
83% match · Dungeon Crawler, Tactical RPG
81% of 474 reviews positive

9·Renowned Explorers: International Society
83% match · Turn-Based, Tactical RPG
92% of 2,910 reviews positive

10·The Banner Saga 3
83% match · Turn-Based Tactics, Tactical RPG
78% of 3,111 reviews positive

11·The Storm Guard: Darkness is Coming
82% match · Tactical RPG, Party-Based RPG
80% of 168 reviews positive

12·For The King
82% match · Tabletop, Rogue-like
88% of 43,857 reviews positive · 321 playing

13·Mortal Glory
82% match · Tactical RPG, Party-Based RPG
87% of 582 reviews positive

14·Blackguards
81% match · Turn-Based, RPG
62% of 3,922 reviews positive

15·Sin Slayers: Reign of The 8th
81% match · Dungeon Crawler, Rogue-like
69% of 91 reviews positive

16·Our Adventurer Guild
81% match · Party-Based RPG, Turn-Based Tactics
95% of 3,635 reviews positive

17·Grotesque Tactics 2 – Dungeons and Donuts
81% match · Dungeon Crawler, Turn-Based
54% of 261 reviews positive

18·AntharioN
81% match · Dungeon Crawler, Turn-Based
69% of 191 reviews positive

19·Depth of Extinction
80% match · Tactical RPG, Turn-Based Tactics
75% of 209 reviews positive

20·Fell Seal: Arbiter's Mark
80% match · Turn-Based Tactics, Tactical RPG
88% of 6,368 reviews positive

21·Bionic Dues
80% match · Rogue-like, Turn-Based
75% of 996 reviews positive

22·Battle Brothers
80% match · Tactical RPG, Turn-Based Tactics
88% of 28,951 reviews positive

23·Card Hunter
80% match · Tabletop, Tactical RPG
85% of 5,333 reviews positive

24·Dungeon Rats
80% match · Tactical RPG, Dungeon Crawler
77% of 724 reviews positive
The closest matches to Popup Dungeon on Steam are The Dungeon Of Naheulbeuk: The Amulet Of Chaos, Dungeon Rushers, Dimensionals, Wildermyth, Age of Fear: The Free World. They rank highest because their Steam community tags overlap most with Popup Dungeon's, and shared tags include Turn-Based Tactics, Dungeon Crawler, Turn-Based.
Every game is described by the tags Steam players vote on it. Rare, specific tags such as Turn-Based Tactics, Dungeon Crawler, Turn-Based count far more than catch-all ones like "Indie" or "Singleplayer", and each game is scored on how closely its whole tag profile matches Popup Dungeon's. Popularity never affects the ranking.