I opened an issue, concerning the previous post, and the developer responded…since SDLTRS 1.2.26 the Model I emulation no longer boots directly into BASIC if there is no disk image specified for drive :0, but asssumes the “Expansion Interface” is “connected”: you have to press BREAK (ESC on the PC) a few times while booting to get into BASIC … or disable the “Expansion Interface” (Floppy Disk Controller) by adding the -nofdc or -nofloppy option on the command line …
So adding -nofdc to my command line startup worked!