You can either get a 4G / 5G outdoor antenna or change your mobile provider hoping it’s better than the old one.

Otherwise, there isn’t much you can do.

What are your devices? If you have Apple only, Books already does everything you need, and you need no self-hosting.

completely free, not self promotion

For the future: The first doesn’t imply the second. In some countries, if I donate to you based on your “free” work, if it’s in the same line of work you do for your main job (e.g. developer) it still counts as income.

But still, tools like these are very useful and I thank you for sharing your efforts!

I second networking. Otherwise, specialize yourself in certain fields and market yourself with respect to them. I specialized myself in some obscure GIS subfield and it brought in a couple of sweet gigs over the course of the years.