Using Uber-H3 from Qgis

There's the official https://github.com/uber/h3-py

Python bindings for H3, a hierarchical hexagonal geospatial indexing system https://uber.github.io/h3/

but I haven't tried it myself.

You can play with it using my #30DayMapChallenge hexagon demo https://github.com/ThomasG77/30DayMapChallenge/blob/master/day4_hexagons/data/h3-processing.py

Except the fact I do no use an UI, I combine both QGIS and Uber H3 Python library.

I clearly do not use all parts of the H3 Python library. I suppose the example could help you getting started.

Use the Create Grid tool in QGIS, and select hexagons.

For a more thorough, but still brief walk-through, see Jonathan Soma's blog.

(This is for creating a hex grid, it will not be specific to Uber's H3 grids. If you know the positioning and spacing of that grid you could use those numbers with this tool.)