If not already shown as supported in the Table of Hardware
https://openwrt.org/docs/guide-developer/adding_new_device
Be aware that anything with less than 16 MB of flash or less than 128 MB of RAM is not an "interesting" device for most people, especially if they don't already own it.
Also relatively unlikely that a Movistar fiber/ADSL router can have open-source support.
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What is your question?