I found some recent videos on YouTube with people that have no internal monologue and/or have aphantasia:
Q&A with a person who does not have an internal monologue
My Girlfriend Has No Inner Monologue or Mind's Eye | Q&A
It's really interesting how different people's brains can work.
A good place I found to practice visualization besides meditation is in the shower. I'd imagine something wholesome such as a tree on a hill overlooking plains in the distance. Visualization is like a muscle. When it's not used for a while, there's only faint images or images that last for only a few seconds, but with practice they can get clearer.
I watched that video with the interview with the person who doesn't have an internal monologue a couple of days ago and found it really fascinating. My own thinking tends to be dominated by a monologue and visualization plays a much lesser role. Picturing something in my mind tends to require more effort.
I especially found it interesting that she seems to have a different view of languages (which she studies), seeing more of their structure and rules rather than a linear type perspective (if I understood it right). I could kind of relate to the way she talks about writing essays - when I'm really 'in the zone' with writing I start to get that sort of perspective - almost like seeing the whole piece as a structure and reordering and changing things from that perspective. When something doesn't fit, or a thought isn't expressed as well as it could be, it's almost like there's an aesthetic issue with the whole structure, like a part of a painting where the perspective isn't quite right.
Anyway, I find this 'different ways of thinking' discussion really interesting.