as much as possible, htmx tries to take HTML to its logical conclusion (from my perspective) as a hypermedia, rather than imposing other ideas on top of it
So it's not really an "Angular-1-like", but more like Vaadin in JS.
we have written a book on the topic here:
you can read chapters 1 & 2 for an overview of what hypermedia is at a systems level:
https://hypermedia.systems/hypermedia-reintroduction/
https://hypermedia.systems/hypermedia-components/
As far as what the term _hypermedia_ means: it is a media, such as a text, that includes within it _hypermedia controls_. Those hypermedia controls allow non-linear branching and interactions with the media, hence the term _hyper_, that is, above, "normal" media, which is consumed passively.
The hypermedia controls we are all most familiar with are anchors/links & and form tags. htmx attempts to generalize the concept of a hypermedia control.
The book goes into gory detail if you are interested in further exploring the idea.
If I had to pick an “Angular-1-like” framework, I would pick the one that clearly documents it’s boundaries and provides a clear way to use a mature SPA framework when there is a need to cross those boundaries. If anyone is aware of such framework, please share.