Most of these things you will find answers in existing threads if you search this forum and the iodé Community forum.
I’ve used the OpenEUICC app to successfully scan in my eSIM from QR Code. But have not tried scanning QR Code with the camera. It will likely depend on the app you are using - I have Open Camera, not the default one, on my BraX3. Some QR codes may not scan if your app doesn’t inherently recognise them.
But also keep in consideration the risks of QR Codes, as touched on here:
Rule of thumb is don’t scan them unless you absolutely 100% are certain they are clean and safe. For me that’s nominally my eSIM from my work telco and possibly that’s it - nothing else.
Also this below is a year old, but might be useful if standard camera app isn’t workable or doesn’t support it:
Again, you will find search useful as there will nearly always be an existing discussion of what you are asking - And in summary generally anything will work its just a question of whether it has any built in reliance on G apps that may reduce it’s functionality when they aren’t present - this has been discussed elsewhere. One obvious example is Android Auto - currently seems impossible to get this fully functional even with all G apps installed on the BraX3 (or possibly any other degoogled phones).
Fitness Apps
I’m going though this myself. Previously have used Apple Health and Garmin Connect (for my watch), and in the past Map My Walk/Map My Run. I’m migrating to a new privacy friendly app that will keep data on my device (for me to download to my Linux PC) and not use cloud storage, and a generic replacement for Garmin Connect (GadgetBridge?). See these threads:
If you decide to try My Fitness Pal and see if it works okay on the phone you should, if you haven’t already, recheck it’s privacy and security - both the policies/statements and any feedback or articles on it. Many of these apps sell all the data or are otherwise notorious for poor security so your location can be easily tracked via it, etc…
WhatsApp
Well - I see you say it’s for work - personally I wouldn’t go near WhatsApp with a barge pole, and won’t have anything meta on my device (as it’s contrary to privacy and security). But that’s an individual choice and plenty of people do put it on - I just can’t understand why (even if its supposedly needed for work)… But that’s just my personal preference. FWIW I use Signal (actually Molly), Session is probably the best overall currently but more complex to use, and Signal is almost as good and has more chance of adoption by large numbers of people (and contrary to popular belief doesn’t require exposure of phone number for people to connect to you, etc). There are other options but they are a bit more obscure - see links below for more info.
If you do need to have it, the best advice I have is to put it into Work Profile with Shelter and freeze it as much as possible and don’t allow notifications - just have a routine of checking occasionally (at a frequency you need to) and refreeze every time. Work Profile and Shelter may not be perfect but it’s the best way I can think of currently to put it on the device and not totally compromise the device to zuckerberg…
Zoom & Teams
I can’t comment on Zoom - another one I won’t personally use. If you check the list I previously shared above (and have repeated below) you will see it’s not on there - so no one has reported it as usable. So you will just have to try it and see I guess. Note that Signal and similar can provide all the functions Zoom does in a more secure environment - but i’m guessing you need this for work again…?
Microsoft Teams I can report works and again it’s on the list I previously shared and reported as fully functional (see the links in my original reply to you and below). You need to put this in Work Profile under Shelter, or in my case it’s in Private Space with Microsoft Outlook as these are the 2 apps I need to have for work, and both are Microsoft, so I just keep Private Space locked (so these apps are frozen) and unlock it as needed for work, or to quickly check messages when out of the office. And obviously lock them down further with permissions (e.g. location) and in the iodé app.