Replace anonymized data in string

Hi Team,

I have some data that has been anonymized and I would like to generate some test data from this. In some way, I would like to deanonymize this data with random data.

For example, phone numbers have been anonymized with changing the 5 right digits with the 8 digit (preserving length).
Applying this, the number 390694802756 was changed to 3906948088888.

I would like to get random digits at the end of the phone number knowing that anonymized data can be a variable length.
So, I would like to change every sequence (at least 2) of 8 by random value of same length (I don't worry if phone number contains 88 in the middle and this sequence is changed to random data)...

I tried to do this with replace / regexp_replace functions but could not achieve what I wanted to do.
I don't want these digits to be changed with a single one (88888 by 111111 or 99999 but something like 42384)...
Ideally, the new string would be different if multiple sequences of 8 appear in a string and would be different from one record to the other when applied to a full table...

Is there any way to do this ?

Thanks,
Patrick