It
is highly recommended to do a healthy amount of research on your
specific mission-critical apps and their compatibility with the OSs you
might be interested in. In my experience and the experiences of most of
my customers, we run into either no issues or very few with the apps we
want to use.
A few exceptions I can list out to illustrate what
owning a degoogled phone is like though are crypto.com's app. There was a
post some time ago on the GrapheneOS forums talking about a few apps
like this one that look at a very obscure field within Android to make
sure the app was installed from the Google Play Store before running at
all. Naturally, something we're trying to do with degoogled phones is
avoid anything Google including the Play Store like the plague, and
using this app without compromising your privacy is something that would
take tremendous skill to execute correctly.
In other cases,
you'll have to experiment with obscure settings and fixes to get some
banking apps working like HSBC's. However, the vast, vast majority of
banking apps work without any problems at all.
I'd say issues
like this are virtually non-existent outside of two main kinds of app.
The first is financial apps like the two listed above, and the other is
ridesharing apps like Uber. While I can't guarantee every single app
will work, I've been shocked by how smooth the degoogled experience can
be most of the time.