Looking around, that square is supposed to be an eye icon from OOUI (example). I think that an 'eye', line should be added somewhere in skin.json, but I'm not exactly sure where. Possibly on line 426, after 'edit', (at any rate, that is where the icon next to the "view on meta" icon is defined).
I don't see any recent commits relating to this. Possibly there was some other code that loaded the eye previously, that recently stopped loading it.

We had a similar issue on T395980: Discussion tools add topic shows in page actions menu without an icon. This should be added by MobileFrontend. @Esanders @DLynch off the top of your head could any changes to names of the editor icons have broken this? I recall we used to show an "eye" for view source.

Nothing has changed about eye in forever. In 2017 it got moved from general icons into the accessibility subset, but that was the last thing that touched it. It's actively in use in VisualEditor itself and outside it in visual diffs, and in both places it's referenced as eye.

I think the answer is just "it isn't in skins.minerva.icons"? That's currently:

"icons": [
	"speechBubbleAdd",
	"edit",
	"wikiText",
	"editLock",
	"history",
	"language",
	"menu",
	"search",
	"userAvatar",
	"userTalk",
	"star",
	"halfStar",
	"unStar",
	"die",
	"heart",
	"home",
	"logIn",
	"logOut",
	"mapPin",
	"settings",
	"userContributions",
	"unStar",
	"watchlist"
]

I'm not sure where it should strictly be being added -- which extension is actually triggering the use of this icon, and whether that should be doing its own addition of the item to something or whether we can reasonable expect that Minerva should be including all the icons the toolbar is likely to use, even the ones that aren't added directly by itself? The DT ticket you mention was resolved in part by just adding the icon that was needed to Minerva's module, so...

I'm not sure where it should strictly be being added -- which extension is actually triggering the use of this icon, and whether that should be doing its own addition of the item to something or whether we can reasonable expect that Minerva should be including all the icons the toolbar is likely to use, even the ones that aren't added directly by itself? The DT ticket you mention was resolved in part by just adding the icon that was needed to Minerva's module, so...

Currently Minerva.
On the long term T379236: Provide a way for extensions to register icons needed by a skin on every page load. I think it's acceptable to add this to skins.minerva.icons for now (patch-welcome).

Looks like I registered the eye icon in 6d1ab8826e04 but did not account for the associated link not being displayed in Minerva. Before that the link was not showing at all, even without an icon so the fact it's showing up at all is at least a step in the right direction.

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Change #1181247 had a related patch set uploaded (by Escargot bleu; author: Escargot bleu):

[mediawiki/skins/MinervaNeue@master] Add eye icon to Minerva skins.minerva.icons

https://gerrit.wikimedia.org/r/1181247

Hi @Escargot_rouge
I have added an eye icon to Minerva Skins. Could you please check my patchset and review it? If you think any improvements are needed, I would be happy to work on them.

https://gerrit.wikimedia.org/r/c/mediawiki/skins/MinervaNeue/+/1181243

~Thanks

Change #1181243 had a related patch set uploaded (by Pppery; author: Aruhi28):

[mediawiki/skins/MinervaNeue@master] Add eye to the list of available actions in skin.json

https://gerrit.wikimedia.org/r/1181243

Change #1181243 merged by jenkins-bot:

[mediawiki/skins/MinervaNeue@master] Add eye to the list of available actions in skin.json

https://gerrit.wikimedia.org/r/1181243

This appears to be working in production: https://test.m.wikipedia.org/wiki/User:Jon_(WMF)

In T401432#11120502, @Jdlrobson-WMF wrote:

This appears to be working in production: https://test.m.wikipedia.org/wiki/User:Jon_(WMF)

Checked on wmf.16 - the icon is displayed in Minerva for

https://test.m.wikipedia.org/wiki/User:Jon_(WMF)	https://fr.m.wikipedia.org/wiki/Fichier:Paris.svg	https://fr.m.wikipedia.org/wiki/Utilisateur:Jembot

Test Result - Prod

Status: ✅ PASS
Environment: enwiki
OS: macOS Sequoia 15.5
Browser: Chrome Canary (latest as of test date)
Device: MS
Emulated Device: iPhone 14 Pro (Minerva)

Test Case 1: Meta user page link in Minerva

1. Open https://fr.m.wikipedia.org/wiki/Utilisateur:Jembot in a mobile browser (Minerva skin).
2. ✅ AC1: The eye icon element is present in the DOM (not a blank square).
3. ✅ AC2: The icon has the correct “eye” class reference from skins.minerva.icons.

4. Open https://fr.m.wikipedia.org/wiki/Fichier:Paris.svg in Minerva skin.
5. ✅ AC3: The eye icon is rendered correctly in the DOM.
6. ✅ AC4: No blank square or missing icon is shown in place of the eye icon.