I find this often with apps and websites, and I speak/write British English (or attempt to).
Why effort is put into making a worse interface is baffling.
I got the same behavior on macOS by using https://github.com/carjorvaz/macos-us-altgr-intl/blob/master...
On mobile I just switch to the hiragana keyboard, but that obviously isn't a sane option on desktop unless I'm clicking all the characters with a mouse?
Assuming Microsoft's Japanese IME is still a dumpster fire, and the Google one has not succumbed to Googleshitification, that would be a way to go.
To enable the Microsoft IME there are some rituals to go through like adding the Japanese language and then a Japanese keyboard under that. It will download some materials, like fonts and dictionaries. A reboot is typically not required, I think, unless you make Japanese the primary language.
Once you have the keyboard, LeftShift + LeftAlt chord goes among the input methods. Ctrl + CapsLock toggles hiragana/romaji input. I think these are the same for Google or MS input.
It might sound complicated at first, but you can do it pretty fast once you get used to it.
https://learn.microsoft.com/en-us/globalization/input/japane...
Standard Qwerty keyboards are well supported, you'll need to either check the key shortcut to switch between inputs or do it with the mouse if it's infrequent enough.
People using it daily will tweak a lot more, have a straight to IME and straight out of IME key instead of the default switching pattern, potentially add more tweaks to always have half-width space and ponctuation whatever the mode they're in etc., but that's a rabbit-hole you'll be free to fall into.
BTW the reverse works well enough: Windows has a specific mode to force US ANSI on JIS layouts and still use the additional japanese keys. Kinda fun they felt the need to leave that mode in.
Native Cantonese speakers in Hongkong have similarly diverse input methods. I've even seen tiny digital draw pads at the public library. It is pretty exciting (to me!) to watch an elderly person furiously scribbling away on the pad, inputting traditional Chinese charaters to search something on the Internet or in the media catalog. I think it is very cool that public library makes a strong effort to empower all types of users.
"shio ha natoriumu[Space][Return][ImeOff](Na)[ImeOn] to enso[Space][Return][ImeOff](Cl)[ImeOn] kara dekite imasu[Return]"
-> "しおはなとりうむ(Na)とえんそ(Cl)からできています"
-> "塩はナトリウム(Na)と塩素(Cl)からできています"
(NOTE: spaces added for legibility)
Most Japanese users use this "romaji" input - which is more vibe heuristics based and not highly consistent with existing romanizations hence the change. Some use "kana" with full 51 Hiragana symbols on JIS keyboard(with ろ/backslash/underscore key to left of RShift, which makes it incompatible with ISO). I think "most people don't do this anymore" remarks refer to the fact that everyone's on the phone, and uses the "flick" input.big if true, jesus christ microsoft
(To differentiate between the case where it's actually two vowels, you have to put an apostrophe inbetween; their example is 小唄 -> ko'uta.)
(The bugs I've experienced: it doesn't properly disable itself during video games, despite claiming to do so; sometimes the popup seem to come up when I swear I didn't press the shortcut keys; rarely, the popup gets stuck on screen and needs to be Alt+F4'ed.)