Microchip has not released an open source debugging tool that can be used freely with GDB. Everything is for their Microchip Studio (formely Atmel Studio) Visual-Studio based IDE.
Success with debugging over UPDI (which is what the ATtiny1626 has) were extremely limited or very hacky. There have been some results in Debug an avr 4809 with microUPDI? - #39 by maxgerhardt as also summarized in UPDI Debugging AVR128Dx with platformio - #4 by maxgerhardt.