I’m sorry, but if you want install any google app or service on e, you don’t have understand for what e was created.
We know, that some banking apps won’t work. But some are working out of he box and some working with this hack [HOWTO] Installing Banking Apps
There will never be a thing which will fit’s for all. If you don’t want swap from gapps to better apps or you can’t live without the baking app, you have to stay with lineageOS or any other custom rom.
Most banks are do have an alternative to pushTAN. Before I have getting my Tan2Go app running I have to use a chipTAN Generator. I think YOUR bank will also use this chipTAN way.