As far as I know, using backspace to go back was something from Internet Explorer, which other browsers copied as a concession to users used to it, but only on Windows. I've used Firefox for over a decade, and backspace never went to the previous page for me, even on a new install, so "every webbrowser for decades" is a stretch.

Firefox on Linux has supported it for ages, too. I’ve used it frequently, at least.

Just because something is and has been standard for a long time, it doesn't make it good UX.

It sucks that it's gone - it took me months to retrain my muscle memory to stop using backspace - but I've definitely accidentally navigated back from a form before.

I've adjusted. It's a hard decision but imo the right one. Future generations shouldn't have to deal with this.

To anyone reading who needs a keyboard-based substitute: Alt+Left Arrow.

[Alt]+[←] requires two hands, though: One to press the [Alt] on the far left of the keyboard, one to press [←] on the far right of the keyboard.

That’s horrible.

I typically use a vim-like set of keybinds when possible, so for me it's something like shift-H or g,h.

That's weird, because I press it all the time with one hand. I don't even reliably use the same hand. Does your keyboard not have an Alt key to the right of the space-bar?

On international keyboards, there is no right alt key, but instead at that place is [AltGr], which triggers both [Alt] and [Ctrl].

[AltGr]+[M] for example gives μ, [AltGr]+[E] gives € and [AltGr]+[Q] gives [@]. Obviously, [AltGr]+[←] doesn't work.

It's one more of those shortcuts that make it obvious that whoever made the decision only ever used a US Standard keyboard, and never even considered international users. The only decisions even worse are ever using ` (it's a 4 key combo on some international keyboards, and not at all existing on others), or ~ \ [ ] { } ( ) ; : (all of these are combinations of usually two or three keys on most international keyboards).