I installed version 3.4.0 and repeatedly searched for the QTILE3(QTiles and QTile , i try both of them) plugin, but failed. Why do not I find this plugin?can anyone help me?
The developers, NextGIS, have not ported this plugin to QGIS3 for their own reasons, and Lutra posted the QTILES3 plugin. Due to copyright issues, this plugin was removed in favor of a more thought out solution. QGIS 3.8 (3.7 Dev) should be able to read/write mbtiles natively through the development of Lutra. See documentation here