Single Parenting Support Group
Today being raised by a single parent is not uncommon. About three in ten children live in a single parent home. The most common type of single parent home is one with only a mother. However, single father homes are the fastest growing type of family situation; 60% growth in the last ten years alone.
Here's a link to one group: https://www.dailystrength.org/group/parents-of-children-with-adhd
And here's a link to another: https://www.dailystrength.org/group/adhd-add
There are other ADHD groups on here, but those two appear to be the biggest and most active.
Best wishes in your search and on your journey.