great, and if you need some help and it is a openproject i could give you a hand on my free time

the backup format that i get from feed43 was basically a url that mounts the feed in one go, exemple:

https://feed43.com/feed.html?action=build&feed_title=Martial%20Peak%20-%20readm.org&feed_link=https%3A%2F%2Freadm.org%2Fmanga%2F16086&feed_description=Martial%20Peak%20-%20readm.org&item_title=Martial%20Peak%20-%20%7B%252%7D&item_link=%7B%251%7D&merge_items=0&global_template=&item_template=Martial%20Peak%20-%20%7B%252%7D&name=6613671012567704&auth=a20c06a907bde2d174aa585812e8d22f&url=https%3A%2F%2Freadm.org%2Fmanga%2F16086&encoding=UTF-8&global_pattern=&item_pattern=%3Ctd%20id%3D%22table-episodes-title%22%20class%3D%22table-episodes-title%22%3E%7B*%7D%3Ch6%20class%3D%22truncate%22%3E%7B*%7D%3Ca%20href%3D%22%7B%25%7D%22%20data-navigo%3E%7B%25%7D%3C%2Fa%3E%7B*%7D%3C%2Fh6%3E

removing the browser encoding, you basically has all the info to build the feed:

https://feed43.com/feed.html?action=build&feed_title=Martial Peak - readm.org&feed_link=https://readm.org/manga/16086&feed_description=Martial Peak - readm.org&item_title=Martial Peak - {%2}&item_link={%1}&merge_items=0&global_template=&item_template=Martial Peak - {%2}&name=6613671012567704&auth=a20c06a907bde2d174aa585812e8d22f&url=https://readm.org/manga/16086&encoding=UTF-8&global_pattern=&item_pattern=<td id="table-episodes-title" class="table-episodes-title">{*}<h6 class="truncate">{*}<a href="{%}" data-navigo>{%}</a>{*}</h6>

feed_title=Martial Peak - readm.orgfeed_link=https://readm.org/manga/16086feed\_description=Martial Peak - readm.orgitem_title=Martial Peak - {%2}item_link={%1}item_template=Martial Peak - {%2}auth=a20c06a907bde2d174aa585812e8d22furl=https://readm.org/manga/16086&encoding=UTF-8item\_pattern=<td id="table-episodes-title" class="table-episodes-title">{*}<h6 class="truncate">{*}<a href="{%}" data-navigo>{%}</a>{*}</h6>