Other than putting in a tall antenna, no. Our house is tucked in a valley behind a hill, which is great for weather resistance and cool summer breezes, but not so great for cell signals or broadcast tv.
Legally, I don't know of anything. The length of coax and the resulting loss of signal issue is what stopped us from putting cellular amplifier in. After going down a few rabbit holes, we eventually came around to the concept of Starlink and WiFi calling. Of course, if you happen to have a better internet solution than Starlink, that would be even better.
One purveyor of equipment pointed out that in the US, it is illegal to repeat a cell signal out of doors without permission from the carrier, but that they had many clients in Mexico that were doing that. Wink, wink... Personally, I have my doubts as to coverage, since reading the specifications most of these amplifiers / antenna pairs have coverage of 1000sq.ft. or so.
All the best,
Peter