Export my Lightroom IOS photos to Dropbox or google drive ?

I'm not really up on this, so someone else may be able to provide you with a better perspective. I don't know how you would do it directly from your IOS device. However, if you are using Lightroom and choosing the option to store a copy locally on your hard drive and then the local copy could be sent to either of those cloud services.

Another possibility is if you are using everything in conjunction with Lightroom Classic so that your images are automatically downloaded to Lightroom Classic, then those images are on a local hard drive and could be copied to those cloud services.

As I indicated, there may be other ways to accomplish what you want to do. I have only offered a couple of suggestions I can think of. I use Lightroom Classic mostly, very little of the IOS stuff.