There are a few posts around here discussing this, you can probably look thru them.
In summary, you now need to additionally
- get your police checks in France done and authenticated and perhaps translate it if necessary
- get your medicals done either in France (harder to figure out, but you save time getting this step done in Taiwan, you time waiting in Taiwan may be around 7 days) or in Taiwan (Easier but you need more time in Taiwan, 7 days for medical results, more time to get residency approved in Taiwan)
- if your mom is no longer a Taiwanese citizen, some kind of proof from a relative (eg. Declaration with ID saying allowing to add you to address) or contract from a landlord as proof of address.
- gather those and the documents you earlier used to get your NWOHR passport and go back to TECO in France or NIA in Taiwan (enter with Taiwan passport) for a residency permit.
- there are several other steps in Taiwan involving going to the HHR office to set up hhr and getting a new passport ( check Calm-narwhal’s reddit post which is more comprehensive).
Some links
https://www.reddit.com/r/taiwan/comments/1cqot8e/foreign_national_here_born_abroad_outside_taiwan/
https://www.reddit.com/r/taiwan/comments/1ezrns7/applying_for_a_定居證副本_from_teco_long_post/