In 2.1, the map is revealed along the flight path of the artillery shell.
Is it possible that one of my other artillery mods is affecting things?

May be. Send the mod list please.

0.4.0 - AAI Containers & Warehouses - aai-containers
0.8.0 - AAI Vehicles: Ironclad - aai-vehicles-ironclad
0.2.9 - Air Scrubber - air-scrubber
0.7.6 - Bigger Artillery (2.1 Port) - alexx-bigger-artillery
2.1.0 - Artillery Equality for Vanilla Only - artillery-equality
2.1.0 - Artillery Visibility 2.1 - artillery-visibility-2_1
1.1.0 - Artillery Shell Stack - ArtilleryShellStack
1.1.2 - Auto Deconstruct - AutoDeconstruct
2.1.23 - Base mod - base
4.2.1 - Biter Cleanup - biter-cleanup
3.3.0 - Blueprint Sandboxes - blueprint-sandboxes
1.0.1 - Circuit Visualizer Fork - circuit_visualizer_fork
1.2.0 - Easy Oil Recipes - EasyOilRecipes
2.6.1 - Editor Extensions - EditorExtensions
2.1.23 - Elevated Rails - elevated-rails
1.0.2 - Epic quality on Fulgora - epic-quality-fulgora
3.2.0 - Even Pickier Dollies - even-pickier-dollies
1.0.0 - Explosive Artillery Fork - explosive-artillery-fork
1.15.0 - Factory Search - FactorySearch
2.1.0 - Filter Mining Drills - FilterMiningDrills
0.17.2 - Factorio Library - flib
0.4.4 - Gleba Pentapods on Nauvis - gleba-on-nauvis-port
1.0.0 - Go Green - go-green
1.0.1 - Improved Robots - improved-robots
2.2.25 - Factorio Standard Library - kry_stdlib
0.2.2 - Railgun artillery - ldinc_railgun_artillery
1.0.2 - Legendary quality on Fulgora - legendary-quality-fulgora
0.3.1 - Loader Mini 1x1 And Box - loader_mini_1x1
21.3.0 - Manual Inventory Sorting - manual-inventory-sort
1.0.2 - Map Reveal Tool for 2.1 - map-reveal-tool-for-21
2026.10.11 - Modlist UI - modlist-ui
2024.12.14 - More Module Slots - more-module-slots
0.0.32 - My Quick Start - MyQuickStart
0.1.3 - Nuclear Scorch Decay - nuclear-scorch-decay
2.3.0 - Omnimover - omnimatter_move
2.0.0 - Pollution module - pollution-module
3.4.3 - Quality of Life research (2.1 fork) - qol_research-21
2.1.23 - Quality - quality
2.1.1 - Realistic Artillery Shells - RealisticArtilleryShells
2.1.23 - Recycler - recycler
9.2.6 - Reverse Factory - reverse-factory
2.1.23 - Space Age - space-age
2.0.5 - K2_TurretsFixed - super_awesome_K2_TurretsFixed-new
1.0.1 - Synthetic Bioflux - synthetic-bioflux-port
2.1.0 - Teleporters - Teleporters
1.3.0 - Turret Range Buff - Percentage - turret_range_tweaker
2.1.2 - Waterfill - Waterfill_v17

The mod only affects the vanilla artillery shell, making it look in every artillery shell would take some time.

Ah, ok. And yes, your mod would be a bit more extensive if it was to account for every arty shell mod.