New Customer Accounts pages do not support RTL (right-to-left) languages such as Hebrew and Arabic. All text and UI elements are left-aligned with no way to customize direction via theme code or CSS. Please add RTL support for New Customer Accounts.
Have not tried myself, but Shopify claims it’s supported – https://help.shopify.com/en/manual/customers/customer-accounts/upgrade/customization-options#brand-and-content
Right-to-left (RTL) layouts are also supported in customer accounts, but translations for RTL languages aren’t provided by default. You can add languages to your store and provide your own translations.
Have you tried to provide translations?
Are your store / market /language choice set up for RTL language?
Can you share a link to the store in question?
yeah this part is real, the new customer accounts pages are hosted by shopify so you can’t drop css or liquid into them like you can on the online store theme. there’s no stylesheet to add direction: rtl to, that’s just how that surface works right now, not a bug.
the direction there actually comes from the locale, not from css. so worth checking: did you add arabic/hebrew as a real language under settings > languages (an actual RTL locale), publish it to the market the customer is on, and is the customer’s selected language set to that one? if it’s a proper RTL locale shopify should put dir=rtl on those pages by itself. if it’s still left aligned, usually the language isn’t really resolving to the RTL locale, or it’s english with translated strings instead of the arabic locale itself.
past what the locale gives you, the only real lever on new customer accounts is customer account UI extensions (app based), since plain css/liquid isn’t available there.
what’s the store url and which RTL language did you add? easier to say what’s off then.