That’s quite unfortunate to hear. I use Bitwarden along with Gboard and very rarely run into issues - I believe most password managers have a quick settings toggle that you can add into your notification drawer to maybe get around this? From what I know though, these generally use the Accessibility framework to function, and thus will heavily depend on your password manager - it also gives a lot more access to those apps than the built in autofill framework.
Conversely I remember Bitwarden’s autofill support on iOS being quirky when I last used it (which to be fair, has been a while - I’m sure its improved since then). IIRC it pretty much always worked in Safari (and Safari Web Views within apps), but the actual applications themselves wouldn’t always give me the autofill prompt.
For me though, regardless of the platform it still is far more worth using a password manager and unique passwords per-site than to use a single password (or even a handful) across sites. I hope autofill support improves for those that it doesn’t work well with.
That is awful, Celiac’s (and really any autoimmune disease) is no joke. I see a lot of parallels reflected in their post and I truly hate that for them so much - constantly struggling to find foods that you can tolerate, having numerous surgeries, seeing a million different doctors, being in and out of the hospital all the time to the point that its a second home, lab test after lab test that only result in more questions than answers, symptoms and other issues spiraling up due to complications of going through the condition - you name it.
I feel for them, every day feels like you’ve got the curse of Sisyphus. I feel like there has to be a solution for people like them and I, and its unfortunate that there is just so much about the body and its various systems that we don’t understand. I constantly struggle with the idea that we’ve come so far with the sciences, and yet it feels like in matters of human physiology like the GI, immune, and nervous system we’ve barely scratched the surface.