The workaround that worked for me on Pixel 8 with Boursobank (iodé 7.1):
Download the app from Aurora Store
Go to Settings → Apps → microG Services → Disable
Go to Settings → Apps → Boursobank → Storage → Clear Storage
Open Boursobank and login (the integrity check error should not appear)
Once logged in, you can re-enable microG Services
Hope this helps!