Dark and minimum userstyle for Wikipedia and Wikidata (or other Mediawiki site, Wikibase). You can set this style at the admin side of Wiki for your account - for "vector legacy (2010)" theme, no browser extension needed.

Link for editing your Wikipedia CSS (remove @-moz-document block, with open and closing brackets).

Missing links to Edit, History, Wikidata - use shortcuts. Also you can append to an url of an article &action=edit, &action=info. Hotkey for Wikidata: Alt-Shift-G. To Edit source: Alt-Shift-E. Edit visual: Alt-Shift-V.

Want to see languages? Add this JS to your global.js and you will have languages at the bottom:

$(function() {
	if (mw.config.get( 'wgAction' ) == 'view') {
		lang = document.getElementById('p-lang')
		document.body.append(lang)
	}
})

About Wikimedia Commons uploading: this CSS hides checkbox with text

I confirm that this work does not include material restricted by copyright, such as logos, posters, album covers, etc

but this checkbox must be checked in order to continue - so you need to use this JavaScript:

    if (mw.config.get('wgPageName') == 'Special:UploadWizard') {
        // "I confirm that this work does not include material restricted by copyright, such as logos, posters, album covers, etc."

        const parent = document.getElementById('upload-wizard')
        const config = { attributes: true, childList: false, subtree: true }
        const observer = new MutationObserver(_ => {
            const node = document.querySelector('.mwe-upwiz-deed-compliance input')
            if (node && node.checked == false) {
                node.click()
                // I tried node.checked = true but it was not enough
            }
        })
        observer.observe(parent, config)
    }