Magic/science crossovers I can think of offhand…

The Madwand series and the Amber series by Zelazny. Actually Lord of Light may sort of qualify too? He was big on mixing the two. Roadmarks is another one.

There’s also people writing about magicians living amongst us. Stuff like the Unseen University by Naomi Novak. Very much traditional magic but also taking place in the modern world. Same for An Unkindness of Magicians by Kat Howard. Actually one of the very best from this genre is The Magicians by Lev Grossman.

I also love Strata by Terry Pratchett which is a suitably hilarious take on building a flat planet where magic works in a science universe.

And another idea I really enjoy is books that have applied the principals of science to magical systems. Probably my favorite is The Craft Sequence by Max Gladstone. Magic is basically something like a stock market/economic system and you end up with index funds of souls and so forth. Very strange but fascinating to think about. Similarly Foundryside by Robert Jackson Bennett is all about using magic as a system and developing new spells based on known principles of that system. (And using them to steal things.)

Gideon the Ninth is necromancers in space. It’s written as a scifi, but the necromancy is a hundred percent magic, not science veiled in mysticism.

Also, The Traitor Baru Cormorant is a hard fantasy. Which isn’t what you asked for, but it’s similar in that it blends both genres.

My first exposure to sci-fi + magic were the Shadowrun novels. I enjoyed reading them years ago, but not sure how well they’ve held up.

Up-vote for the Well World books! I remember them fondly. It’s been 40 years – might be time for a refresher :) Now I see he wrote two more in the series in 1999/2000? I had no idea. Suppose I have no choice now