How can I set up home WiFi to overcome dead spots from thick stone walls?

My house is about 130 years old, a time when everything was made with thick stone walls (\~40-60cm). It has three storeys and is fed by 600Mbps fiber on one side of the middle storey. I currently only have one router sending wifi to most the middle floor, and the signal travels well to the upper storey through a wood floor. But it doesn’t penetrate well below, where it meets a concrete floor, nor to the far side of the house where it hits thick stone walls with few doorways through them.

I’d love some general advice on setting up a mesh WiFi network (or other ideas) to get some signal to those dead spots. I understand from browsing this sub that you guys hate wireless connections, but I cannot drill through these walls to run cable. The walls continue through the ceilings the whole height of the house too. I understand wireless compromises speed but my priorities are reach and stability for casual internet use/streaming throughout the home.

Thanks in advance!

EDIT: Forgot to mention there is no coax either! There used to be a phone line that came in where the fiber does now, in the corner of the window, but I removed it because idk it’s 2026.