Problem between ionic storage and localForage about ionic-storage

[thiboot]

This is a warning because the package localforage (wich is used by ionic-storage) does not use completely ECMA Script Modules.
localforage is not maintained since last release : Aug 18, 2021 ...

Maybe it's time for ionic team to find a better alternative

[Samuel-Therrien-Beslogic]

localForage/localForage#977 was reverted due to IE11 support breakage.
In the mean time you can re-apply it yourself using patch-package. Doing the modification yourself and running npx patch-package localforage --exclude 'nothing' should produce the following patch:
patches/localforage+1.10.0.patch

diff --git a/node_modules/localforage/package.json b/node_modules/localforage/package.json
index f3c8fbc..27b0627 100644
--- a/node_modules/localforage/package.json
+++ b/node_modules/localforage/package.json
@@ -63,6 +63,7 @@
         "webpack-dev-server": "^1.10.1"
     },
     "main": "dist/localforage.js",
+    "module": "src/localforage.js",
     "typings": "typings/localforage.d.ts",
     "bugs": {
         "url": "http://github.com/localForage/localForage/issues"

Then add npx patch-package to scripts.postinstall in your package.json to always re-apply the patch on install.